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Sustainability in Coal and Mineral Mining Operations is need-of-the-hour

We define sustainability in mining as mining and mineral development that meets the growing needs of all communities while maintaining a healthy environment and vibrant economy for present and future generations.

The Criteria in Sustainability in Mining can be applied to mineral exploration and mining projects/operations as follows: 

  1. Health and Safety: The project/operation is acting to ensure the health and safety of workers and the community.
  1. Effective Engagement: The relationships with those affected by a project/operation are characterized by integrity and trust.
  1. Respect for Indigenous Peoples: The project/operation respects the rights, culture and values of Indigenous Peoples.
  1. Environment: Actions are being taken to ensure the maintenance and strengthening of environmental integrity over the long term within the region of influence of the project/operation.
  1. Full Mine or Operation Life Cycle: A full mine or operation life cycle perspective is being applied for planning and decision making that spans exploration through post-closure.
  1. Resource-use Efficiency: The project/operation is seeking to minimize resouce inputs—energy, water, reagents, supplies, etc.—while also minimizing contaminant outputs to air, water and land.
  1. Continuous Learning and Adaptation: The uncertainty inherent in mining operations is recognized, and a commitment to continuous learning is displayed.
  1. Benefits: The project/operation is enhancing the potential for creating economic, social and cultural benefits for the local community or region.

The   importance of sustainable development principles has been increasing within the mining sector over the past two decades. Early work focused mainly on mining metals and commodities other than coal and energy fuels. Because sustainability, however, is an important consideration for all human endeavors now, the coal industry has become active in sustainability efforts. A number of global coal mining companies have embraced sustainability as a key aspect of corporate philosophy.

Continued production of minerals and fossil energy fuels may not fit into commonly understood definitions of sustainability. Mineral and energy extraction and reclamation operations do, however, contribute significantly to sustainability through the benefits they provide to society, when they are conducted in a manner that supports sustainable economies, social structures and environments throughout all phases of mining, including closure.

Significant progress can also be made through the inclusion of sustainability concepts in the original design of the operation, as well as in ongoing operations. Innovative engineering, mining and reclamation operations can be optimized through consideration of environmental and economic sustainability goals, side-by-side with traditional technical mining engineering considerations.

It is widely recognized that coal is and will continue to be a crucial element in a modern, balanced energy portfolio, providing a bridge to the future as an important low cost and secure energy solution to sustainability challenges. In response,  the  global  coal  and  energy  production industries have begun a major effort to identify and  accelerate  the  deployment  and  further  development  of  innovative,  advanced,  efficient, cleaner  coal  technologies.  A  number  of  coal producers  are  also  involved  in  sustainable  development  activities,  including  economic  support of communities and regions, environmental restoration and social well-being.

The designer of, specially, coal mining operations needs to simultaneously consider legal, environmental and sustainability goals along with traditional mining engineering parameters as an integral part of the design process. The role of coal in the global energy supply mix makes this of primary importance. There is a need for research into the parameters for mining design that allow the building of models for optimization, the relationships between those parameters, and the desired outcomes that the system is being optimized to produce. In addition to quantifying the economic viability of the operation, a number of sustainability goals should be built into the model and the relative importance of those goals determined.

Sincerely,

Partha Das Sharma

E.mail: sharmapd1@gmail.com

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Differential Energy blasting technology

The trial of Dyno Nobel’s Differential Energy blasting system at a U.S.gold mine was a major success; improving fragmentation, reducing fumes and increasing ore production.

Dyno Nobel’s proprietary Differential Energy explosive delivery technology allows mine operators to precisely vary the characteristics of the bulk explosive in the borehole to match rock properties and address specific needs. The system is delivered through specially designed bulk trucks using proprietary down-the-hole automatic gassing technology with Dyno Nobel’s Titan® ΔE 1000 bulk explosive.

In the trial, the blasting technicians were able to precisely load three different energy density segments into the borehole. The aim was to optimise the energy distribution by placing the higher energy profile at the bottom of the blasting hole, normal energy profile in the middle and lower profile energy at the top.

The trial showed Differential Energy increased overall shovel productivity by 8%, reduced powder factor by 18%, eliminated the need to dewater wet drill holes and reduced all visible NOx after-blast fumes over traditional blasting methods.

http://www.mineweb.com/mineweb/content/en/mineweb-technology?oid=206008&sn=Detail

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Safety in Mines – Unique, “Fatigue Monitoring System” can detect dangerous fatigue in heavy machine operators

Alert and Activeness of heavy mining machines operators (specially in mine truck drivers) while in operation is the key to safe operation of machines. In other words, operators should never ever feel drowsy when operating heavy vehicles. Yet, such things happen in mines, with unwanted disastrous results.

However, thanks to a new invention from an Australian company that will warn when operators are just a little bit too tired for their own.

The invention goes by the practical name of the Fatigue Monitoring System, and it’s the creation of a company called Seeing Machines, based in Canberra. Using an infrared camera designed strong enough to see through sunglasses, and an image-processing computer to analyze the frequency, duration and speed of the driver’s blinking to assess inattention and the probability of imminent “microsleeps”. Thus, Fatigue Monitoring System pays close attention to the eyes of those operating heavy duty vehicles to check for signs of tiredness that could lead to accidents down the line.

More than seventy percent of accidents involving drivers of the three-story-high, 400-ton, open-pit mining trucks are said to involve fatigue.

An U.S. heavy-equipment maker Caterpillar says it’s installing a $10,000 Australian-developed system that can monitor drivers for fatigue in all its mining trucks.

Ref:

http://www.digitaltrends.com/cool-tech/fatigue-monitoring-system/

https://mining.cat.com/fatigue-monitoring

http://www.energy-business-review.com/news/caterpillar-seeing-machines-sign-deal-for-fatigue-monitoring-systems-in-mining-machines-290513

http://www.upi.com/Science_News/Technology/2013/05/28/Monitoring-system-can-detect-dangerous-fatigue-in-mine-truck-driver/UPI-24481369776695/

http://announce.ft.com/Detail/?DocKey=1323-11596061-2DNT2GNGUTT3JCK27LK632RNG6

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Blast Induced Ground Vibration
The energy released at the blast site is sufficient to cause permanent changes to the rock mass. This area is typically less than 35 hole diameters. For example, a 3-inch diameter hole would cause fracturing that extends out approximately 105 inches or almost 9 feet. Outside of this area the energy is elastic, so that the particles of the Earth are not permanently deformed or displaced. After the energy passes the particles return to their original resting position.

As particles of the Earth are displaced, these particles impact other particles which impact other particles, and as this process continues, the energy is transmitted away from the blast site. This transmission of energy flows as a wave. An analogy would be the effect of dropping a stone into a pool of water. At the point of impact, the water is displaced sufficiently to produce individual droplets that separate. Past the impact point, the energy can be seen travelling away as waves.

As the energy travels outward from the source, it diminishes or attenuates. With increasing distance, the affected area greatly increases and the energy becomes widely dispersed. In general, the amplitude of the vibration can be expected to decrease by approximately two-thirds for every doubling of the distance.
1

Frequency of Vibration:
Frequency is used to describe the oscillating nature of the vibration. We tend to talk about a vibration as being composed of cycles. Frequency is mathematically determined by taking the inverse of the time it takes to complete one cycle. This value is commonly expressed in Hertz (cycles per second). The red highlight in the image represents one cycle that lasts about 0.2 seconds. The frequency of this cycle would be 1 divided by 0.2 seconds which equals 5 Hertz (Hz). Frequency plays an important role in how individuals perceive ground vibration and how structures react to ground vibration.

Human Perception on Ground Vibration:
Beginning in the 1930s, research was conducted with volunteers to determine sensitivities to vibrations. Although people are sensitive to sounds and vibrations, it is difficult to quantify perceptions. Inside a structure, people will feel the building shake and hear the objects around them rattle such as windows and knick-knacks on walls. When an event is perceived, some people will say that they felt very strong vibrations, even if the vibration was too low to be felt outside. The reactions of people are best understood when observed in their own homes during times of real-life events. These reactions may not be the same as those of volunteers under controlled conditions.

Human response to blasting is subjective, as two people will react differently to the same vibration event depending on where they are in a structure, their frame of mind and their personality. Unfavorable reactions to vibrations may often result in complaints. When residents feel a blast, they may become concerned about damage to their home.
The threshold peak particle velocity of ground vibration perception is about 0.51 mm/s (0.02 in/s) for most people. This is 1/100 of the limit of 50 mm/s (2 in/s) commonly used for construction blasting or in reference to below the chart bounds.

Structure Response on Blast Induced Ground Vibration:
Residential structure response to blast vibration has been researched extensively (Example: USBM RI 8507 and RI 8896). And frequency is a very important component of ground vibration because it affects how structures respond. The general types of response within a structure caused by external vibrations are:
• Foundation Structure Response or the structure vibration below the ground level is equal to the incoming ground vibrations.
• Whole-Structure Response or the racking motions, of the above ground part of the building, that respond to frequencies of 4 Hertz to 12 Hertz.
• Mid-Wall Response or motions within individual panels or components of the above ground part of the building, normally out of plane with walls, responsive to frequencies of 12 Hertz to 20 Hertz.

2In the whole structure response, the above ground portion of the structure is free standing, and moves more than the below ground portion because the foundation is fixed. Differential motions between the upper and lower corners cause racking responses. Mid-wall responses are typically responsible for window rattling, picture tilting, etc.

When the vibration frequency closely matches a natural or fundamental frequency of a structure or structural component, the structure or component will tend to respond more vigorously and the incoming ground vibrations are amplified in the upper portion of the structure. Alternatively, if the ground vibration frequency does not match the natural frequency, very little seismic energy transfers into the structure, and there will be little, if any, response.

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Controlling Vibration damage and Airblast from Blasting:

Vibration Damage Control Criteria

The U.S. Bureau of Mines recommends the following:

  1. Particle velocities of less than 51mm./s (2.0 in./s) show little probability of causing structural damage.
  2. If there is at least 8 ms. (millisecond) separation between detonations, the vibration effects of individual explosions are not cumulative.
  3. Particle velocity is still the best single ground motion description.
  4. Damage potential for low-frequency blasts (< 40 Hz) is considerably higher than that for higher blasts (> 40 Hz).
  5. Practical safe criteria for blasts that generate low frequency ground vibrations are 19 mm./s (0.75 in./s) for modern gypsum board partition houses and 12.7 mm./s (0.50 in./s) for lath and plaster interiors. For frequencies above 40 Hz, a safe particle velocity maximum of 51 mm./s (2.0 in./s) is recommended for all houses.
  6. Human reactions to blasting can be the limiting factor. Vibration levels can be felt that are considerably lower than those required to produce damage.

Controlling Airblast

Excessive airblast is controlled by ensuring that all charges are properly confined. Excessive airblast is generated by the same poor confinement conditions that cause flyrock. Conditions that cause high over-pressure levels:

  1. Inadequate stemming
  2. Mud or weak seam venting
  3. Inadequate burden confinement
  4. Poor blasting timing
  5. Focusing by wind or temperature inversions
  6. Uncovered detonation cord
  7. Overloading

Air blast from detonating chord trunklines can be significantly reduced if it is covered with at least 20 cm. (8 in.) of dirt or sand. Non-Electric shocktube blasting is much safer and controls Air-blast.

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Surface wave intelligent profiling system (Swips) to improve drilling and blasting practices in Mines

Scientific equipment supplier and software developers based in Canada have developed the surface wave intelligent profiling system (Swips) – a revolutionary and patented Technology to the mining industry that enables the users to visualize and characterize the physical and mechanical properties of solids – for the rapid characterisation of geological structures beneath the earth’s surface to improve drilling and blasting practices.

Swips is a nonintrusive technology based on seismic surface waves that enable its user to visualise, analyse and model the physicomechanical properties of solids. The system’s maximum depth in optimised conditions is 500 m.

The Swips can be applied as a pathfinder to reduce drill holes in the prospecting phase. It can also be used to do ore characterisation, blasting operation, blasting effect monitoring, mine design monitoring and roof and slope monitoring, while geotechnical applications, include building and structure evaluation.

For more: www.micromentis.com/

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LOW DENSITY, POROUS AMMONIUM NITRATE GRANULES (for ANFO) – Cost effective Low Cost Technology:

Introduction: Ammonium Nitrate (AN) is well known for its Explosive qualities. Possibility of conditioning it the form of small balls having a diameter usually between 1 and 3 mm renders it very easy to use as a civil explosives employed in quarries, mines etc. It is usually mixed with 94.0% AN and 6.0% FO by weight. The presence of Hydrocarbon has for effect of sensitize the nitrate, i.e., to permit it to detonate more easily by the effect of sympathy with an initiating explosives. To permit the absorption of hydrocarbon by the AN, these are made porous. Generally, to create porosity in AN prilling is done by putting AN solution at the top of Prilling tower then recovering AN prill at the lower part of the tower .  The required porosity is obtained during drying by elimination of water.

Granulation process of producing low density porous ammonium nitrate – In this process a granulator, which is a rotary drum, and a fluid bed are employed for production of porous granules. The process comprise of spraying Ammonium Nitrate solution in this granulator and effecting a combined cycle of granulation and drying, which causes formation of pores in the mass of granules. The drying is then terminated in a drier and product thereafter screened and cooled. The granules thus formed are spherical in shape, smooth, hard and porous and do not breakdown easily during handling. This process has particular advantages in preparing granules for use in ANFO composition.

Main advantages :

¢  - No more prilling tower,

¢  - Less air to scrubber and better pollution control,

¢  - Lower Capital Investment.

Results :

¢  - Final product humidity : 0.25%

¢  - Density : 0.7 – 0.8 gm/cc

¢  - Granulometry : 90% between 1.7 and 2 mm

¢  - Oil absorption : 8%

Ref:

  1. US Patent No. 6022386
  2. US Patent No.US 2009//0301618A1

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New generation Safer and Eco-friendly Primary Explosives, ‘Nickel Hydrazine Nitrate (NHN)’, likely to replace ASA in Commercial Detonator manufacturing:

Nickel Hydrazine Nitrate (NHN) is evolving as a new generation high energy material, which is likely to replace Lead Azide & Lead Styphnate (ASA) as primary explosives used for detonator manufacturing. Nickel hydrazine nitrate, a chemical that is 30 per cent less sensitive compared to conventional chemicals ASA.

NHN is a thermally and hydrolytically stable solid, easily prepared from available raw materials. Its preparation liquor can be used repeatedly, which means no waste-water pollution in industrial manufacture. NHN is not sensitive to impact, friction, or electrostatic charge, but is more sensitive to flame. It is demonstrated that NHN is suitable as a replacement for lead azide as an intermediate charge in commercial detonators.

On the other hand, detonators are usually made with the composition of ASA. These chemicals are highly sensitive to friction/impact and are thus more prone to accidental explosions.

As NHN is a less sensitive and eco friendly primary explosives, substitute for ASA as a primary explosive can be used in varied detonator applications, specially, for use in blasting in mines and construction industry.

Refer:

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Ventilation in Underground Mines where Diesel-powered mobile equipment runs:

The main objective of mine ventilation is the provision of sufficient quantities of air to all the working places and travel ways in an underground mine to dilute to an acceptable level those contaminants which cannot be controlled by any other means.

Where depth and rock temperatures are such that air temperatures are excessive, mechanical refrigeration systems may be used to supplement the beneficial effects of ventilation.

The composition of the gaseous envelope encircling the earth varies by less than 0.01% from place to place and the constitution of “dry” air is usually taken as 78.09% nitrogen, 20.95% oxygen, 0.93% argon and 0.03% carbon dioxide. Water vapour is also present in varying amounts depending on the air temperature and pressure.

The contaminants to be controlled by dilution ventilation are primarily gases and dust, although ionizing radiations associated with naturally occurring radon may present problems, especially in uranium mines and where the background uranium concentrations of the host or adjacent rocks are elevated. The amount of air required for dilution control will depend on both the strength of the contaminant source and the effectiveness of other control measures such as water for dust suppression.

The minimum dilution air flow rate is determined by the contaminant requiring the greatest dilution quantity with due cognizance of the possible additive effects of mixtures and synergism where one contaminant can increase the effect of another. Overriding this value could be a minimum air velocity requirement which is typically 0.25 m/s and increasing as air temperatures also increase.

Diesel-powered equipment ventilation

In mechanized mines using diesel-powered mobile equipment and in the absence of continuous gas monitoring, exhaust gas dilution is used to determine the minimum ventilation air requirements where they operate. The amount of air required normally ranges between 0.03 and 0.06 m3/s per kW of rated power at the point of operation depending on the type of the engine and whether any exhaust gas conditioning is being used. Continuing developments in both fuel and engine technology are providing lower engine emissions while catalytic converters, wet scrubbers and ceramic filters may further reduce the leaving concentrations of carbon monoxide/aldehydes, oxides of nitrogen and diesel particulates respectively. This helps in meeting increasingly stringent contaminant limits without significantly increasing exhaust dilution rates. The minimum possible dilution limit of 0.02 m3/s per kW is determined by the carbon dioxide emissions which are proportional to engine power and unaffected by exhaust gas conditioning.

Diesel engines are about one-third efficient at converting the energy available in the fuel to useful power and most of this is then used to overcome friction resulting in a heat output which is about three times the power output. Even when hauling rock up a decline in a truck, the useful work done is only about 10% of energy available in the fuel. Higher diesel engine powers are used in larger mobile equipment which require bigger excavations to operate safely. Allowing for normal vehicle clearances and a typical diesel exhaust gas dilution rate of 0.04 m3/s per kW, the minimum air velocities where diesels operate average about 0.5 m/s.

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Organic Catalyst Treatments: Eco-friendly and safer technology

Organic catalysts improve environmental waste treatment in a number of critical maintenance and processing areas.

Key attributes that make organic catalysts uniquely attractive are its ability to elevate the level of dissolved oxygen (DO) in solution, regardless of aeration technique; ability to solubilise the molecular structure of organic wastes, including the insoluble fats, oils, and grease (FOGs) components; eliminating chronic and dangerous volatile organic compounds (VOCs), such as ammonia and H2S gases; and the ability to enhance biological nitrogen removal (BNR) systems.

Sewers: Maintaining aerobic environments within collection systems is essential to avoid chronic service problems and dangerous conditions due to hazardous gases, which are also the source of most public complaints. Eliminating slime layers and FOG clogging are excellent maintenance applications for organic catalysts. They can also be used to increase dissolved oxygen levels within gravity and forced mains, as well as other aerobically compromised parts of the system.

Aeration Systems: Organic catalysts has been shown to make a substantial improvement in aeration systems through raising dissolved oxygen levels, increasing gas transfer rates, and improving bioprocesses. Improving aeration system performance can lower energy requirements (up to 30%), along with acting as a method for maintaining higher dissolved oxygen (DO) levels during heavier loading periods, which provides operators with a means to better manage optimum microbiological activities.

Sludge Processing: Processing of bio-solids can be substantially improved with addition of organic catalysts. Sludge volumes have been significantly reduced (up to 40%) while methane production quantities were maintained in full-scale applications. Subsequent treatment and handling of bio-solids can be improved due to reduction in odour and better bio-processing of the bacterial components.

Technology Breakthrough: Organic Catalysts have undergone extensive and independent testing, showing the highest safety for human, animal, and marine life. Organic Catalysts are non-toxic, non-caustic, non-corrosive, non-irritating, hypoallergenic, bacteria-free and biodegradable.

This safety profile provides significant competitive advantages against traditional chemicals, including biological agents, due to their unsurpassed handling ease and safety for workers.

Organic Catalysts are comprised of a fermentation supernatant, derived from plants and minerals, which is blended synergistically in combination with a non-ionic surfactant to create a broad spectrum bio-organic catalyst. Unlike conventional surfactant, which can limit oxygen transfer, Organic Catalysts self-organize and create heavy micro bubbles having very high oxygen transfer characteristics. More available oxygen enables aerobic reactions that will speed up the natural degradation process, while improved gas transfer rates improve both the conversion of insoluble organic waste components to carbon, and enhance maximum utilization of molecular oxygen.

Organic Catalysts provide economically compelling benefits to environmental professionals, bringing practical and cost saving advancements to wastewater treatment, water clarification, industrial and commercial cleaning; and have also shown great promise in agriculture, biofilm eradication, and hydrocarbon remediation applications.

Ref:

http://www.mining-technology.com/contractors/health-and-safety/ecocatalysts/presswhen-are-organic-catalysts-treatments-useful.html?WT.mc_id=DN_PR

http://www.mining-technology.com/contractors/health-and-safety/ecocatalysts/presstechnology-breakthrough-organic-catalyst-treatments.html?WT.mc_id=DN_PR

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Perimeter blasting (Contour blasting) in Tunnels and construction activities using Electronic Detonators:

In all excavation profile is very important, more so, for tunneling. A good profile in excavation, means lesser back-break. Moreover, in construction blasting or in tunneling, good profile implies that the fractures induced into the host rock by blasting of contour shots donot exceed design limits, thus restricting operation of supporting, spraying and waterproofing to be bare necessary.

The contour is improved by designing the blast, specially the contour shots as follows:

* Making sure that holes are accurately parallel at the fullest extent

* Narrowing hole spacing to bare minimum

* Using detonating cord or explosives of a type specially suitable for the purpose, loaded in diameter substantially smaller than the holes

Blasting theory provides another useful hint – to obtain a profile coinciding as much as possible with design profile, simultaneous firing of all contour shots. Generally, in tunnel contour shots are primed with high delay numbers which fire with substantial scattering. Only Electronic Detonators can provide real simultaneity in firing of contour shots, to achieve better profile. Since simultaneity in explosion is the essential prerequisite for quality of contour blasting, it may be economical to use Electronic Detonators for the purpose.

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Sequence of Multiple Face Technique of Large Cross Sectional Tunnel Excavation

Early knowledge of rock structure and strength is used in the design tunnel of an openings shape, and excavation method. In large civil construction tunnels, rock quality is used to specify opening sizes, excavation method, round length, and ground support requirements. Large highway tunnel faces are often split into multiple headings that are advanced with specified offsets from one another.

By advancing and supporting a series of small headings, large unsupported spans of ground are never exposed, and ground failures are reduced.

Example: A 3.6 by 5.5-m (12 by 18-ft) centre drift was excavated first and supported at the final tunnel perimeter with bolts and shotcrete. Subsequent side slash and centre cut sections were then excavated and supported in the sequence shown below.

sequence_tunnel

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Rock Fragmentation by Blasting – Blast Fragmentation Models on Monte Carlo-based Simulator increases understanding of the effects of Rock Mass and Explosive properties.

Rock fragmentation is considered the most important aspect of production blasting because of its direct effects on the costs of drilling and blasting and on the economics of the subsequent operations of loading, hauling and crushing.

Over the past decades, significant progress has been made in the development of new technologies for blasting applications. These technologies include increasingly sophisticated computer models for blast design and blast performance prediction.

Apart, rock fragmentation depends on many variables such as rock mass properties, site geology, in situ fracturing and blasting parameters and as such has no complete theoretical solution for its prediction. However, empirical models for the estimation of size distribution of rock fragments have been developed.

Blast fragmentation models based on Kuz–Ram fragmentation model on Monte Carlo-based simulator are quite effective in understanding of the effects of Rock Mass and Explosive properties. System can predict the entire fragmentation size distribution, taking into account intact and joints rock properties, the type and properties of explosives and the drilling pattern.

This understanding translate into improvements in blasting operations, its corresponding costs and the overall economics of open pit mines and rock quarries.

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General guidelines of Charging and Blasting in Hot Strata condition:

* Select the number of holes properly so that the total blasting operation should not exceed 2 hour from charging of first hole.

* Measure the temperature of the holes almost constantly till the commencement of blasting operation.

* Use water at least 12 hour before blasting to flush hot holes till the temperature comes down below 80oC.

* Record the temperature of holes at a regular interval of time.

* Use a mixture of Bentonite, Sodium Silicate and Water in holes which do not retain water to seal micro-fractures and cracks. Guar gum upto 5 percent may also be used for the purpose.

* Only slurry or emulsion explosives, preferably bulk explosives to be used for hot-hole blasting purpose.

* It is preferred that explosives charging may be started near the initiation point first, (i.e., load explosives in the sequence in which the blast will be fired first). This allows the pattern to be quickly charged, tied up and fired in the event of a change in conditions.

* Where possible hottest holes to be loaded last.

* Detonating fuse as initiation system only should be used. Shock tube and detonators should not be used down-the-hole.

* Adequate non-combustible stemming material should be available near the collar of each hole prior to commencing of charging operation, for fast accomplishing charging operation.

* Punctured holes are to be plugged at bottom before charging. Air-bags may be used for the purpose.

* Combination of Bulk-Loading Emulsion explosives, Detonating Fuse with ‘Top-Priming’ of Booster is preferred. These primers are applied shortly before blasting time, at the top of the explosives charge, where the emulsion is relatively cooler.

* After primers are put, stemming and firing are done as quickly as possible, without wasting any time.

Precaution:

Water gas – Water gas is a mixture of carbon monoxide and hydrogen, both highly flammable, and is produced in a reaction between hot carbon and water (while putting water on hot coal for quenching purpose). The chemical equation for this is:

C + H2O = CO + H2.

It is highly explosive over a wide range of concentrations (4% to 74%).

For further study on the subject refer: Blasting of Hot Holes in Opencast Coal Mines

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Use of Explosives & Blasting in mining and civil is profitable not only in time and cost savings, but in terms of energy and the reduction of air emissions – As compared to Mechanical means:

In recent years, various research works have been published that reflect concern about carbon dioxide emissions. These studies have made clear that the use of explosives is three times more profitable in terms of energy consumption than digging, for example.

The below table, obtained from a variety of bibliographical sources published in recent years, shows how this comparison provides information that is both curious and surprising.

As the table above shows, energy savings from the use of explosives in blasting compared with excavation and grinding by mechanical means are really significant. Even more so are the financial savings this represents. But perhaps the most interesting aspect is the importance of the use of explosives in terms of reducing greenhouse gas emissions. The table shows how the use of energy materials reduces carbon dioxide emissions by up to 8 times compared with excavation by mechanical means and up to 40 times compared with rock grinding by the same means.

Thus the use of explosives should be recognized as a form of energy with low pollution levels and, its use should be promoted. If all public works used explosives, carbon dioxide emissions to the atmosphere would be significantly reduced. Their use should therefore be given priority for environmental reasons.
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Bulk Emulsion Explosive Enhances Blast Efficiency in UG Metal Mines:

Repumpable Bulk Emulsion Explosive or Underground Bulk System (UBS) as it is generally called, can increase blast performance, reduce costs and enhance safety in Metalliferous Underground Mining operations.

In UBS, the nonexplosive emulsion is transported as a chemical to the mine site, stored in silos or tanks at the shaft head or underground and is then sensitised and pumped into the blast-holes using a specialised delivery unit.

The emulsion explosive is a high-energy product, designed to fire in underground holes and is viscous so that it can be charged into up-holes without running back out.

The emulsion is classified as non-explosive so there is no need for special magazines or secure storage facilities either on surface or underground.

The emulsion is sensitised and becomes an explosive only when it is pumped into a blast-hole.

The emulsion can be transported using regular mine equipment without requiring specially-licensed explosives vehicles, and shaft time can be used in efficient way, since the emulsion can be transported at the same time as other materials.

Additional advantages are gained by the fact that the emulsion is waterproof. Where a mine is wet or faces are mined down-dip, most holes will contain water after drilling. When using an emulsion explosive, holes do not need to be dewatered.

Bulk explosive fills the cross-sectional diameter of each hole, resulting in better utilisation of energy and efficient transfer of the shockwave into the rock mass.

Labour productivity is also increased when using bulk emulsions in underground, due to its quick and easy transportation and short charging times.

Thus, reduction in overall mining costs with efficiency through drill pattern expansion, improved breakage, reduced manpower requirements and accurate explosive charging for precision blasting.

Applications:

* Hard rock underground blasting

* Ring blasting and underground bulk blasting

* Shaft sinking

* Tunnelling in hard rock

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GROUND VIBRATION, SCALED DISTANCE, PREDICTOR EQUATION AND DETERMINATION OF SAFE CHARGE PER DELAY

  • When blast holes are under or over charged and absence of proper free face a great deal of liberated energy is wasted and converted into ground vibration, as explosion energy is not utilized in fragmenting / breaking of rock and throw.
  • Broadly speaking, the key factor that controls the amount and type of blast vibration produced is EXPLOSIVES ENERGY CONFINEMENT and THE DISTANCE OF THE STRUCTURE FROM THE BLASTING SITE.
  • On this basis the concept of Scaled Distance equation has been developed:

                                         Distance of Structure from blast site

Scaled Distance = ————————————————————–

                                          Max. Charge wt. Per (8 ms) delay interval

USBM PREDICTOR EQUATION:

V = K (D/Q½)-B

Where, ‘V’ is the peak particle velocity, ‘D’ is the distance of the measuring transducer, ‘Q’ is the maximum charge weight per delay and ‘K’ and ‘B’ are site constants to be determined by regression analysis.

D/Q is known as SCALED DISTANCE.

Regression Analysis: Taking Logarithm of both sides of the Predictor equation, we get:

Log V = Log K – B Log (D/√Q)

If,  Y =  Log V;    X =  Log (D/√Q) and   C = Log K; then the above equation represents a straight line of the form   Y = C –  BX  (Straight Line  plotted on Log V as Y axis and Log (D/√Q) as X axis below);  where B is the negative slope of the straight line and C is the point of interception on Y axis.

CRITERIA FOR LIMITING SAFE VIBRATION LEVEL:

Now the prime objective is to determine the maximum charge to be fired per (at least 8 ms) delay interval, in order to keep PPV within the safe limit. Following are the procedures involved:

  •  Measurement of PPV with different scaled distances.
  •  Plotting these values on a Log – Log scale as described in figure.
  •  The value of site constants K and B are to be determined by extrapolation of straight line plotted as described above.
  •  Using propagation straight line, safe scaled distance to be determined to keep PPV below safe limit (on the basis of threshold limit prescribed by DGMS, India).
  •  From the determined safe scaled distance above, the maximum charge per delay can be found out for various distances for a particular site.

Besides peak particle velocity, the Frequency is one of the most important factors controlling the response of structures.

Ref:

Explosives, Ground Vibration and Air Blast

Ground Vibration Problem in Openpit Mega Blast

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A Note on Velocity of Detonation (VOD), Strain Energy  (SE) and Gases or Bubble Energy (BE)of Explosives

Detonation velocity is the speed at which the reaction front moves forward through a cylindrical charge. Given that the VOD is the only measurable magnitude related to an explosive that can be given a number with certainty, it is easy to comprehend why it has been overemphasized as an indication of explosive strength. VOD is a function of the explosive configuration, hole diameter and confinement. Hole diameter and confinement are generic environment variables for any given blast. The same explosive in different environments will manifest different VODs.In their literature, manufacturers usually quote the unconfined VOD of a small sample of explosive in a small diameter.Rather than strength, VOD gives a relative indication of the energy partitioning between shock and heave. The higher the VOD, the higher the shock component in relation to the total energy. While low VOD explosives will shift the energy partition towards a higher proportion of heave. In any case, the VOD would have to be measured in a real borehole situation in order to be meaningful. In-hole VOD measurements differ greatly from the values quoted in standard literature.

Understanding theory of detonation of explosives – The self-sustained shock wave produced by a chemical reaction was described by Chapman and Jouquet as a space. This space of negligible thickness is bounded by two infinite planes – on one side of the wave is the unreacted explosive and on the other, the exploded gases as shown in the figure below:

There are three distinct zones:

a) The undisturbed medium ahead of the shock wave,

b) A rapid pressure at Y leading to a zone in which chemical reaction is generated by the shock, and complete at X,

c) A steady state wave where pressure and temperature are maintained.

This condition of stability condition for stability exists at hypothetical X, which is commonly referred to the Chapman- Jouquet (C-J) plane. Between the two planes X and Y there is conservation of mass, momentum and energy.

Velocity of detonation (VOD) of explosive is function of Heat of reaction of an explosive, density and confinement. The detonation pressure (unit in N/m2) that exists at the C-J plane is function of VOD of explosives. The detonation of explosives in cylindrical columns and in unconfined conditions leads to lateral expansion between the shock and C-J planes resulting in a shorter reaction zone and loss of energy. Thus, it is common to encounter a much lower VOD in unconfined situations than in confined ones.

In fact, selection of Explosives for Mining activities are governed by Properties of rock mass, Degree of fragmentation and displacement desired. Most important properties of Explosives are: Strain or Shock Energy  (SE) and Gases or Bubble Energy (BE) produced, water resistance, density, Velocity of Detonation (VOD) and Critical Diameter. The SE / BE ratio influences mode of failure and varies with explosives composition and Velocity of Detonation. The VOD provides the shattering action needed for maximum fragmentation. Detonation impedance which is a measure of the relative ability of different explosives to transmit their pressure to stress wave in a given rock is product of Density and VOD.

The performance of an explosive not only depends on its total energy but also on rate at which it is released. The VOD of an explosive controls its rate of energy released. It also influences the energy partitioning with respect of Shock and Heave (Gas) energy of explosives.

Thus, faster VODs are appropriate in strong rock where a shattering effects are required, and slower VODs are applicable where heaving effects are more desirable than a rock shattering effect.

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Rock breakage by Detonation and Interaction of explosive energy with rock:

Rock fragmentation by blasting is achieved by dynamic loading introduced into the rock mass. The explosive loading of rock can be separated into two phases, the shock wave and gas pressure phase (Fig. A).

The detonation of an explosive charge in a blast hole gives rise to a strong initial shock wave which then decays into stress waves, P- and S-Waves, in the surrounding rock mass, initially as compressive strain waves radiating from the blast hole. In a plane normal to the axis of the blast hole, the stress wave can be considered to have radial and tangential components of stress (Fig.B). The high pressure to which the rock is exposed shatters the area around the blast hole, the crushed zone, and exposes the space beyond that to high tangential strains and stresses. The crushing continues until the stress has been attenuated to below the dynamic compressive strength of the rock. When the compressive wave meets a free surface it is reflected back to the hole as a tensile wave and a shear wave. If the tensile stress, of the reflecting wave, is greater than the dynamic tensile strength, spalling will occur.

The gas pressure phase is a much slower, quasi-static, process than the shock wave phase, which takes place within a few milliseconds. Even if the stress caused by the explosive gases is much lower than the stress caused by the shock wave, it can still fracture the rock mass due to the lower loading rate. The explosive gas pressurise the borehole and applies a radial compressive stress, sufficiently large to initiate and propagate cracks. The high pressure gas penetrates the primary radial cracks, and natural cracks, and extend them further, the free rock surface in front of the blast hole yields and is moved forward. This is how the rock is broken in rock blasting. Thus, fragmentation of rock by blasting is a rapid disintegration of rock. In blasting practices the rock is exposed to both low loading rate, “static”, and dynamic loading.

For rocks there is a huge different between the intact rock strength, here rock strength, and the rock mass strength, which consists of both intact rock and the discontinuities within the rock mass. The mechanical behaviour of rocks spans over a wide range of scale, from microscopic cracks to regional fault systems. Dependent on the issue in consideration different properties of the rock mass controls the strength.

As discussed, on detonation of an explosive charge, the rock immediately surrounding the blasthole is crushed, owing to explosion pressure because of shock energy. The outgoing shock wave, after passing through the crushed zone, travels at between 3000 m/s to 5000 m/s and sets up tangential stresses that produce radial cracks. The pressure produced by the expanding shock wave from the blast source is compressive. The extent of the shock zone around blast hole is nearly 2 to 4 times the radius of blast hole. When the shock wave reaches a free face, it then reflects back toward the blasthole at a lower pressure but in the form of a tension wave through the rock transition zone (Fig.- B). The extent of this zone is 20 to 50 times the radius of blast hole.

The crack density in the transition zone controls the distribution of the fragment size. The explosives with high VOD induces more stress in transition zone thereby increasing crack density. The increase in crack density reduces fragment size. Therefore, it is necessary to use explosives having suitable VOD, in order to get optimize the fragmentation in a mine. It has been observed that, by using pumpable bulk emulsion explosives in place of ANFO, cost of secondary blasting, mucking and crushing is reduced considerably in a hard rock open-pit mining.

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Crater Theory in Blasting:

Crater theory defines an optimum burden or distance to a free face at which a spherical explosive charge is buried and produces the greatest volume of broken and excavatable rock. This distance is unique based on rock type and explosive type. The theory also defines the critical depth or spherical charge buried depth at which surface disturbance is barely detectable, resulting in slight surface mounding and minor cracking.

In a series of experiments it was discovered that a spherical charge broke a much greater volume of rock than a cylindrical charge of the same mass. A spherical charge is defined as a charged that has a ratio of charge diameter to charge length less than 1:6.

If a sufficient number of tests are carried out involving detonation of a fixed amount of charge at various depths in the rock, then the strain energy factor can be calculated from the following empirical equation:

Where, E = strain energy factor, which is a constant for a given combination of explosives

B = Critical distance in metres (the depth where a full crater forms, that is, a conical cavity whose sides meet the horizontal surface at 450), in metres.

Q = Charge weight, kg

It follows that when an explosive charge of constant mass and shape is placed at different distances from a flat free face and detonated, the amount of rock blasted is related to the depth of burial of the charge.

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Determination of Explosive Strength by Underwater Detonation:

Since the 1970s, the underwater detonation test increasingly has been applied for determination of the strength of explosives, especially those that are not cap-sensitive.

The test is of particular importance because it enables the determination of strength of explosives that cannot detonate completely when a charge mass in less than 10gm (that means that they could not be tested by ballistic mortar or lad block test).

By this method, the strength of an explosive is determined on the basis of measurable forms of energy released by underwater detonation – Shock wave energy and Bubble energy.

The method is based on the detonation of an explosive charge by means of a detonator or via a booster at a defined depth under the water surface, and on recording the Shock wave-time profile and Bubble-pulse period at a given distance from the explosive charge.

From shock wave-time profile, the Shock wave Energy is calculated, whereas from bubble-pulse period the Bubble Energy is calculated.

The sum of the shock wave energy and bubble energy gives the TOTAL ENERGY of the explosives.

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EXPLOSIVES AND BLASTING ECONOMICS:

The economic analysis of the use of explosives is an important part of blasting operations in mining and construction. Explosives are energy, and the efficient use of this energy is a major factor in keeping rock blasting costs under control. High-energy explosives enhance fragmentation, which ultimately produces a positive effect on production costs. The degree of fragmentation or movement obtained is directly related to the type of operation and amount of explosive energy applied to the surrounding rock. Analysis of the cost of explosives requires that the effects of explosive energy be placed into proper perspective within the entire drilling, blasting, handling and processing operation. This relationship is illustrated in the following figure:

Efficient blast designs combined with the proper choice of explosive can produce better fragmentation with associated lower operating costs compared to blast designs and explosives used under adverse conditions. As a result, the efficient use of explosives, along with the proper borehole diameter selection, is the keys to a successful blasting program.

Cost of Explosives Energy- The only way to evaluate accurately the cost of explosives, is to examine the effects of blasting and to determine the optimum degree of fragmentation. In most cases, the productivity rate is influenced by the degree of fragmentation. To obtain well-fragmented rock by blasting, explosive energy must be well distributed throughout the rock. To be effective in rock blasting, this energy must be applied at the proper millisecond delay interval to allow for optimum rock movement.

The type and cost of explosives will vary from one operation to another, dependent upon many conditions. The geologic formation, such as hard seams, cap rock, hard bottom, or large toes, dictates the use of high-energy explosives. Water-filled boreholes require the use of water-resistant products at a premium cost. The cost of a product upgrade to cope with wet conditions is an obvious input. Other variables, such as the size of mucking equipment and drilling equipment, fragmentation tolerance, and production demands, will also influence the choice of explosives.

Although a significant recurrent expense, the cost of explosives is usually only a small percentage of the total costs encountered in breaking, moving, and processing rock and ore. The small difference in the cost of a higher energy explosive is insignificant compared to a decrease in production caused by insufficient fragmentation.

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ENERGY FACTORS OF EXPLOSIVES CHARGED IN BOREHOLE FOR BLASTING:

The energy factordescribes the energy distribution within a given unit of rock. Energy distribution within a shot is measured by the energy factor, which compares the explosive energy to a quantity of rock broken. The explosive energy distribution within the entire blast is then evaluated along with its resulting fragmentation and its effect on operating costs. Blasting analysis next becomes a function of the energy factor, explosives cost, fragmentation results, and subsequent production.

Proper energy distribution is important in obtaining the desired fragmentation and movement of the bottom or toe portion of the shot. Energy distribution becomes an important factor when wet holes are encountered, as cartridged explosive products must be smaller than the borehole diameter to allow for easier loading. The resulting decrease in the diameter of the explosives column, reduces the amount of explosive energy within the borehole. The blaster must use higher energy explosives to balance the lost energy.

Necessary explosive energy adjustments at the borehole can be made to compensate for excessive toe, hard bottom, or cap rock. In addition, higher energy explosives can be substituted for lower energy explosives to increase the energy distribution within the rock, thereby increasing fragmentation. However, if fragmentation was satisfactory before the introduction of additional explosive energy, the improved energy distribution within the shot will allow for an expansion of the drilling pattern, with resultant decrease in overall drilling costs.

Improved production rates and consequent cost reduction in digging, hauling, crushing, or moving rock are the major benefits obtained from the efficient application of explosive energy. There are other benefits from better fragmentation, such as reduced secondary blasting, reduced power consumption at the crusher, and less wear and maintenance on equipment with less down time.

Explosive efficiencyis the ratio of the amount of energy released to the calculated thermochemical energy. Emulsions are highly efficient explosives, due primarily to their microscopic particle size. In contrast, explosives with varying particle size, such as ANFO or water gels, will not have a uniform burning rate, and therefore, will not be as efficient. Studies comparing the calculated thermo-chemical energy to the measured energy by the under-water bubble energy technique have shown that the emulsions released 93 percent of the calculated thermo-chemical energy. Water gels with varying particle sizes achieved only 55 to 70 percent of their calculated thermo-chemical energy. The explosive efficiencies of ANFO, and particularly of high-density ANFO, range from 50 to 80 percent of their calculated energies. As a result, emulsion explosives are not only thermo-chemically efficient, but are cost-efficient as well.

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Drillability and Blastability are the geological influences in hard rock drill and blast:

The drillability is not only decisive for the wear of tools and equipment but is – along with the drilling velocity – a standard factor for the progress of excavation works and blasting performance. The estimation of drillability in predicted rock conditions might bear an extensive risk of costs. Therefore, an improved prediction of drilling velocity and bit wear would be desireable. The drillability of a rock mass is determined by various geological and mechanical parameters.

Drilling velocity is dependent on a lot of geological parameters: Those principal parameters include jointing of rock mass, orientation of schistosity (rock anisotropy), degree of interlocking of microstructures, porosity and quality of cementation of clastic rock, degree of hydrothermal decomposition and weathering of a rock mass. Drilling bit wear increases with the equivalent quartz content. The equivalent quartz content builds the main property for the content of wear-relevant minerals. For various groups of rock types different connections with the equivalent quartz content could be detected. In sandstone bit wear is also dependent on porosity or the quality of the cementation.

Rock Blastability: The term “blastability” is used to indicate the susceptibility of the rock mass to blasting and is closely related with the powder factor. An attempt to relate blastability to rock and rockmass properties has been reported Lilly (1986). The blastability index (BI) is defined as:

Where, RMD = Rockmass description, JPS = Joint plane spacing, JPO = Joint plane orientation, SGI = Sp. Gravity influence and H = Hardness (Moh’s scale of hardness).

Rating of different parameters is given in following tables. ANFO powder factor and Energy factor consideration has been given with BI in the graph (as per field data).

Note: A BI value of 100 refers to a massive, extremely hard, iron-rick cap rock. It has a Sp. gravity of 4. Soft, friable shale has an index around 20.

Ref: Lilly,P.a., (1986), An empirical method of assessing rock mass blastability, Proc. Large open pit mining conf. (J.R.Davidson ed.), The Aus. IMM, Parkville, Victoria, October pp. 89-92.

For further study on the subject refer:

* Blast Fragmentation Appraisal-Means to Improve Cost Effectiveness in Mines

* Concept of Blastability – An Update

* Artificial Neural Network Method of Rock Mass Blastability Classification

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STRENGTH OF EXPLOSIVES:

1. Absolute Weight Strength (AWS) : This is the measure of the absolute amount of Energy (in Calories) available in each gm. of explosive.

Example:

Absolute Weight Strength (AWS) Type of Explosives
a.       680 cal/gm Emulsion blasting agent A
b.      912 cal/ gm ANFO (94:6)
c.       550 cal/gm Slurry column charge
d.      620 cal/ gm Slurry prime charge
e.      1080 cal/ gm Ammonium gelatin dynamite

2. Absolute Bulk Strength (ABS) :  This is the measure of the absolute amount of Energy (in Calories) available in each cubic centimeter of explosive. It is obtained by multiplying the AWS by density of the explosives.

3. Relative Weight strength (RWS) : This is the measure of the energy available per weight of explosives as compared to an equal weight of ANFO. It is calculated by dividing AWS of the explosives by AWS of ANFO and multiplying by 100.

Example

a.       Emulsion blasting agent A            =  680 / 912  x   100   =  75 %

b.      ANFO                                                   = 912 / 912 x 100 = 100 %

c.       Slurry column charge                      = 550 / 912 x 100 =  60.30%

d.      Slurry prime charge                         = 620 / 912 x 100 = 67.98%

e.      Ammonium gelatin dynamite      = 1080 / 912 x 100 = 119%

4. Relative Bulk Strength (RBS): This a measure of the energy available volume of explosives as compared to equal volume of Bulk ANFO at a density of 0.81 gm/cc.  It is calculated by dividing the ABS of an explosive by the ABS of Bulk ANFO and multiplying by 100.

Example

a.       Emulsion blasting agent A =  (680 cal/gm x 1.25 gm/cc) /  (912 cal/gm x 0.81 gm/cc)  x  100  =  115 %

b.      ANFO            = (912 cal/gm x 0.81 gm/cc) / (912 cal/gm x 0.81 gm/cc)  x  100   = 100 %

c.       Slurry column charge = ( 550 cal/gm x 1.15 gm/cc) / (912 cal/gm x 0.81 gm/cc)  x   100  =  85.62 %

d.      Slurry prime charge = (620 cal/gm x 1.16 gm/cc) / (912 cal/gm x 0.81 gm/cc)   x  100  =  97.35 %

e.      Ammonium gelatin dynamite = (1080 cal/gm x 1.20 gm/cc) / (912 cal/gm x 0.81 gm/cc)  x  100 =  175%

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Four basic surface firing patterns

The firing pattern is a tool to break and fragment a mass of rock in the most effective way for further handling and treatment in the mining or quarrying process. Although there are a lot of different patterns used in the industry, most of them are derived from the following four basic designs:

1. Row by Row - This firing pattern can be applied in a pure Row-by-Row initiation sequence with delay times only between rows or in a pattern with short delay times between holes and long delay times between rows so there is no interaction between the rows. This design requires at least one free face.

2. Chevron - In a Chevron firing pattern the delays between holes and rows are chosen so that the firing sequence results in a V-formation. By using different delays, the angle of the V-formation can be modified. The Chevron design requires at least one free face.

3. Echelon - The Echelon firing pattern is simply one half of a Chevron pattern. Echelon pattern requires at least two free faces.

4. Diamond - Diamond firing pattern is used for box cuts, sump blasts and other applications where there are no free faces parallel to the blast holes. The broken rock will be displaced upwards, with an increased risk of fly-rock.

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FLY-ROCK ISSUES IN BLASTING:

Analysis indicates that lack of blast area security, flyrock, premature blasts, and misfires are the four major causes of blasting-related injuries in surface mining operations. Flyrock and lack of blast area security issues continue to pose problems for blasters.

Generally, flyrock is caused by a mismatch of the explosive energy with the geomechanical strength of the rock mass surrounding the explosive charge. Factors responsible for this mismatch include:

* Abrupt decrease in rock resistance due to joint systems, bedding layers, fracture planes, geological faults, mud seams, voids, localized weakness of rock mass, etc.

* High explosive concentration leading to localized high energy density,

* Inadequate delay between the holes in the same row, or between the rows,

* Inappropriate blast design,

* Deviation of blast holes from its intended directions,

* Improper loading and firing practice, including secondary blasting of boulders and toe holes.

a) BURDEN: Insufficient burden is a primary cause of flyrock from a highwall face. Blasters need to visually examine or laser profile the highwall face and search for zones of weakness, backbreak, concavity, unusual jointing and overhang.

b) BLAST HOLE LAYOUT AND LOADING: Any deviation in the direction of a blast hole can reduce or increase the burden. While loading a hole, blasters must frequently check the rise of the explosives column to prevent overloading due to the loss of powder in voids, cracks, or other unknown reservoirs. Such overloading will generate excessive release of energy.

c) GEOLOGY AND ROCK STRUCTURE: Sudden change in geology or rock structure can cause a mismatch between the explosive energy and the resistance of the rock. It is prudent to try to detect such changes in advance and adjust accordingly.

d) STEMMING: Stemming provides confinement and prevents the escape of high-pressure gases from the borehole. The stemming should provide resistance to the escape of high-pressure gases comparable for that of the burden. Improper or inadequate stemming can result in stemming ejections. Insufficient stemming also causes violent fragmentation of the collar zone resulting in flyrock and airblast.

e) DETONATOR FIRING DELAY: Critical elements of any blast design are firing delays between adjacent holes in a row and also those between successive rows. The firing delay is a function of the burden, spacing, hole depth, rock type, and the quantity of charge fired per delay. Proper firing delay helps to achieve good fragmentation of the blasted material. It also reduces ground vibration, air blast, and flyrock.

f) LACK OF BLAST AREA SECURITY: An analysis of blasting injuries indicates that several factors are involved in causing injuries due to lack of blast area security. These factors are: (i) failure to evacuate the blast area by employees and visitors; (ii) failure to understand the instructions of the blaster or supervisors; (iii) inadequate guarding of the access roads leading to the blast area, or the secured area; (iv) taking shelter at an unsafe location, or inside a weak structure. Blast area security issues could be addressed by providing adequate training and refresher courses to the blaster and other involved employees.

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Influence of geology on OC blast performance

It is well known fact that, geology plays a very important role deciding performance in OC blasting. OC blasting performance and its adverse effects, to a great extent depend on various geological parameters such as, strata condition, dip, jointing, compressive strength, presence of disturbances etc., of the site. Geology of the blasting site is one of the most important uncontrollable factors to be considered for blast-design purpose. For deciding optimum fragmentation, geological information of the site is needed. Geologic information also needed during mine planning stage, before selection of drilling equipments as well. However, rock mass information is utilized by explosive engineer most to improve blasting efficiency.

Blasting performance in relation to geology of blast site – For every successful blast, explosive energy level and explosive distribution must be matched with geologic condition of the strata to be blasted. Designing of initiation timing sequence must be done in relation to rockmass response to explosive used. Information and understanding of geology of the blast site and its strata condition needed to carryout these adjustments made by blast designer for achieving better result. Experienced blasting engineers are aware of geologic conditions that affect the blast results.

It has been recognised that, fragmentation is the most significant problem encountered by blasting engineers. Generation of over-size is the universal problem in blasting. Sources of generation of over-sizes are as given below, and their possible control measures:

(a) Hard massive boulder in the stemming zone: This problem can be addressed in several ways, such as, placing small explosive decks in the stemming zone which help to overcome this problem by proper distribution of explosive energy closer to the massive layers at the top, satellite holes placed between the production holes also have the same effect of proper distribution of explosive energy near hard strata, and reducing spacing and burden in some case.

(b) Bedding plane slabs from within the blast: This problem causes when blast dimension, hole burden and spacing are much larger than joint spacing. Explosive energy is dissipated within the rockmass through weak bedding planes, so that areas between holes are not effectively fragmented. This problem can be checked by reducing blast dimensions and substituting a higher energy explosive product. This problem may also be aggravated because of insufficient stemming, as the explosive gasses are not confined for a sufficient time they cannot produce the expected breakage within the rockmass.

(c) Hard rock at / near intrusive dykes: Softer dyke rock absorbs the explosive energy. Explosive energy is also being lost along the dyke contact, where open weathered fractures are common. By reducing the blast dimensions or by substituting a higher energy explosive product this problem can be minimized.

(d) Rock isolated from explosive energy by excessive over-break: Measures to reduce back-break include, allowing more time before the last row of holes fires by proper delay timing sequence, design blasts for more movement resulting in less confinement, or cushion blasting the last row of holes.

For more info refer: Characteristics of Rock and Geology influence Surface, UG and Tunnel Rock Blasting Results

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Problem of unintentional and premature detonator firing in Mines

Frequently accidents in mines are caused by the unintentional premature firing of explosives caused by extraneous electricity – stray current or voltage, static electricity or high-frequency irradiation. Ideally, a detonator should be immune to any type of extraneous electricity but unfortunately, this is not possible with conventional electric detonators.

Electronics safer than electrics: Now Electronic Detonator system has taken a huge step forward to creating a safe environment with a solution that provides protection against all kinds of extraneous electricity. Unlike conventional electric detonators, Electronic digital-coded detonator system uses a built-in capacitor to fire the fuse head. Charging and firing are controlled via an electronic system integrated into the microprocessor of each detonator. Only when this chip receives a digital-coded signal can the capacitor be charged to the required firing voltage. After charging the capacitor, an additional specific digital code must be delivered to the detonator to release an electronic switch, allowing the capacitor to discharge and initiate the fuse head.

Immune to inadvertent ignitions: Electronic detonator provides protection against accidents caused by extraneous electricity:

* Safe against Radio Frequency (RF): unparalleled safety against high-frequency irradiation

* Safe against stray current and voltage: far superior to electric detonators

* Safe against static electricity: unaffected by electrostatic discharges, e.g. in the human body

* Safe against induced power caused by lightning: immune to stray current from a lightning strike when the gun system is in the hole

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Autonomous Haulage System (also known as Robotic or informally as Driverless Trucks)

Autonomous Haulage System (AHS) is a comprehensive fleet management system for mines. The dump trucks, which are equipped with vehicle controllers, a high-precision global positioning system (GPS), an obstacle detection system and a wireless network system are operated and controlled via a supervisory computer, enabling them to be unmanned. Information on target course and speed is sent wirelessly from the supervisory computer to the driverless dump trucks, while the GPS is used to ascertain their position. When loading, the dump trucks are automatically guided to the loading spot after computing the position of the bucket of the GPS-fitted hydraulic excavator or wheel loader. The supervisory computer also sends information on a specific course to the dumping spot.

From a safety perspective, the fleet control system prevents collisions with other dump trucks, service vehicles or other equipment at the mining site. In case an obstacle detection system detects another vehicle or person inside the hauling course under AHS operation, the vehicles will reduce speed or stop immediately, making the system extremely safe and reliable.

In addition, AHS enables stable operation under gruelling conditions such as at high altitudes or in sparsely populated, arid desert areas. At the same time, by optimizing operations, the system contributes to reducing maintenance costs, conserving energy and curbing CO2 emissions.

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Challenges before Mining Industry:

Products of the mining industry generate the majority of energy used, from electricity in homes to fuel in vehicles. Mined resources also serve as inputs for consumer goods and the processes and services provided by nearly all other industries, particularly in agriculture, manufacturing, transportation, utilities, communication, and construction.

The mining industry contains five main industry segments, which are defined by the resources they produce: oil and gas extraction, coal mining, metal ore mining, nonmetallic mineral mining and quarrying, and support activities for mining.

Mining industry faces a number of challenges in the near future. Working conditions in mines, quarries, and well sites can be unusual and sometimes dangerous. Some of the mining challenges including quarrying closer to cities and civil structures and greater quarry depths with highwalls subjected to more rock stress and water pressure. In addition, more underground operations that are inherently more dangerous. They are damp and dark, and some can be very hot and noisy. In underground mining operations, unique dangers include the possibility of cave-in, mine fire, explosion, or exposure to harmful gases. In addition, dust generated by drilling in mines still places miners at risk of developing serious lung diseases.

In mechanized system of mining, large, powerful sophisticated equipment moving thousands of tons of ore and rock, round the clock operation, poorly lighted entries, and adverse weather conditions all contribute to the hazardous nature of mining. Hazards arise from equipment design flaws, deficient mine design, or human error. The potential for health and safety risks introduced by new technologies must be addressed proactively. Of particular concern is to understand the system requirements and specifications and to address human interface issues involving the operation, maintenance, and repair of the equipment as well as the computerized control of equipment. Since a truly autonomous mining system is still a future vision, current mining machines will be used for many years. A continuous need exists to reduce equipment hazards, improve component and system reliabilities, and minimize the occurrence of unplanned catastrophic accidents.

Moreover, loss of experienced mine workers due to retirement, an influx of new, inexperienced workers in more challenging mining conditions is one of the most important aspects. Effective training is needed to reduce injuries of both experienced and inexperienced workers from ever increasing diverse background. Mining challenges can be met with better training, using interactive mediums or even virtual reality techniques. The awareness and involvement of the whole workforce needs to be fostered by management, labor and government jointly identifying risk factors, selecting mining practices, implementing mining plans and engineering and administrative controls.

Surface mining requires large areas of land to be temporarily disturbed. This raises a number of environmental challenges, including soil erosion, dust, noise and water pollution, and impacts on local biodiversity. Environmental clearance of Mining, Oil and Gas Fields Projects etc., is becoming more stringent everyday. That is understandable and acceptable, but what is more alarming is the lack of skill sets required to handle such challenges that can come from different agencies such as the department of environment, department of forest etc. By carefully pre-planning projects, implementing pollution control measures, monitoring the effects of mining and rehabilitating mined areas, the mining industry minimises the impact of its activities on the neighbouring community, the immediate environment and on long-term land capability.

Recently, the mining agenda has changed, as the world has taken the carbon-cutting culture to its heart. New challenge is to implement measures to ensure mining operations sustainable, around the world.

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Longwall Mining system capable of achieving high productivity in UG with safety:

Longwall mining is a highly productive underground coal mining technique. System consists of multiple coal shearers mounted on a series of self-advancing hydraulic ceiling supports. The entire process is mechanized. A typical longwall mining system is capable of extracting between 10,000 and 30,000 tons of coal in a day from a panel. Productivity is now higher for longwall mining than for other underground production methods, and productivity is expected to keep growing as new technological advances are introduced.

Longwall mining also offers improved safety through better roof control, more predictable surface subsidence, and better opportunity for full automation.

The primary downside to this very productive technique is a prohibitive initial investment.

Two key factors contributing to the dramatic rise in longwall productivity over the past decade are (1) changes in longwall panel dimensions, and (2) improvements in longwall equipment. Longwall panels have become significantly wider and longer. The use of larger panels also reduced the frequency with which the longwall equipment must be moved from a mined-out panel to a new panel. The move towards larger panels was made possible by improvements in longwall production equipment.

In addition to changes in panel dimensions and longwall equipment, there have been changes in the geologic conditions under which longwalls operate. Particularly important has been the clear trend away from thinner seam longwall mining. Since thin seam longwalls tend to be less productive than thicker seam operations, this development contributed to the overall improvement in longwall productivity.

Thus, merits of Longwall mining Comprises of (a) enhanced resource recovery (about 80% contrasted with about 60 percent for Room and pillar method), (b) less roof support consumables required, (c) elevated volume coal clearance systems, (d) less amount of manual handling, (e) Subsidence is mainly instant, allowing for enhanced planning and more responsibility by the mining concern, (f) safety of the miners is enhanced by the reality that they are for all time under the hydraulic roof supports when they are tacking out the coal.

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Challenges in addressing Safety of Programmable Electronic Mining Systems:

The trend worldwide in Mining industry is to depend increasingly on programmable electronic (PE) systems in safety-critical applications. The mining industry is utilizing this technology to improve safety and health, to increase productivity, and improve competitive positions. PE technology, (i.e., software, programmable logic controllers (PLC’s) and microprocessors), have unique technical and managerial challenges for system design, verification, operation, maintenance, and assurance of functional safety. This technology has unique failure modes different from mechanical or hardwired electronic systems traditionally used in mining. Apart, PE also adds a level of complexity that, if not properly addressed, can adversely affect worker safety.

PE-based mining system mishaps typically involve multiple factors including complex interactions of software, hardware, humans, and the application environment. It is expected that complex interactions will become more problematic as the complexity and sophistication of PE based mining systems escalate. Addressing system complexity effectively is need-of-the-hour. In fact, less complex systems are safer, have fewer systematic errors and are easier to verify for safety.

Ref.: http://www.cdc.gov/niosh/mining/pubs/pdfs/atsop.pdf

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Eco-friendly Pulse Powered “Plasma Rock Fragmentation” method

There is a great deal of interest in fragmentation of rocks in such areas as tunneling, quarrying and mining. Conventionally, blasting by explosives is the usually employed method in excavation work. Due to problems of vibration, noise, and scattering of stones, this method is prohibited of use near important buildings and residential areas. The alternatives to this method are breakage by such crushing machines as large breakers and by chemical substances. However, such breakage methods are high in cost and the problems of decrease in breaking performance were observed.

Plasma Blasting Technology (PBT) involves the production of a pulsed electrical discharge by inserting a blasting probe in a water-filled cavity drilled in a rock, which produces shocks or pressure waves in the water. These pulses then propagate into the rock, leading to fracture.

Compared with conventional blasting method such as rock drilling machines, the PBT technology is friendlier to the earth, because it causes less vibration, noise, and dust, and uses no chemical substances. In the blasting procedure, a reusable blasting electrode and a power supply main body incorporating capacitors and other devices that are connected by a cable are used.

Newly developed compact blasting equipment is suitable for blasting of platy structures and boulder stones. Holes for blasting can be opened by hand-held tools. Therefore, the blasting procedure is easy and simple. By creating more than one hole in linear orientation and discharge at the same time, the object can be blasted as if it were cut.

This compact blasting equipment is suited for following applications.

* Blasting of thin, platy object (structures such as buildings and furnaces).

* Blasting of boulder stones. Digging of riverbed.

* Use in places where transportation of heavy load is difficult (such as mountains, slopes, and high places).

* Flexible and imprompt blasting under various situations (such as recovery work in a time of disaster).

* In the case where blasting like cutting is required, such as finishing of the blasted surface after main excavation work.

The main features of the PBT technology are as follows.

* Low vibration, low noise.

* No scattering of stones.

* No chemical reaction.

* Discharge portion is reusable.

* Blasting in the sea is possible.

* No heavy machinery is required.

For more refer: Pulse Plasma Rock Fragmentation Technology

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Patent for Eco-friendly ‘The Electro-Mining Technology’ for direct extraction of Copper granted:

Patents for the Electro-Mining process have been issued in Chile, South Africa and China and are pending in the United States, Canada, Australia and Brazil.

As per conventional process of extraction of copper, copper bearing minerals are concentrated from crushed ores by froth flotation or bioleaching. Heating this material with silica in flash smelting removes much of the iron as slag. The process converts iron sulfides into oxides which in turn react with the silica to form the silicate slag which floats on top of the heated mass. The resulting copper matte is then roasted to convert all sulfides into oxides. The cuprous oxide is converted to blister copper upon heating. This step reduces the copper oxide to copper metal. Natural gas is blown across the blister to remove most of the remaining oxygen and electro refining is performed on the resulting material to produce pure copper.

The Electro-Mining Technology subject to the patent revolutionizes copper extraction technology by bypassing nearly all of the traditional copper extraction process, which is expensive, time consuming and environmentally unfriendly and extracts copper directly from crushed raw material using an electrical and chemical process that allows the copper to diffuse through the raw material and attach to a steel plate submerged in a chemical solution.

In other words, the technology extracts copper directly from crushed raw material using an electrical and chemical process.

The process is more environmentally friendly as the chemical solution is contained in plastic tanks, water and acid are recycled in a closed system.

Above Electro-Mining Technology is owned by Fast Cooper.

Ref.: http://www.steelguru.com/metals_news/Casablanca_Mining_subsidiary_granted_electro_mining_patent_in_China/214372.html

http://www.reuters.com/article/2011/07/11/idUS127703+11-Jul-2011+BW20110711

http://www.mining-technology.com/news/news124204.html?WT.mc_id=DN_News

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Management of topsoil is essential for geo-environmental reclamation:

Soil is the non-renewable natural resource, which supports life on earth. Topsoil is an essential component for land reclamation in mining areas. It is seriously damaged if it is not mined out separately without being contaminated, eroded and protected. Systematic handling and storage practices can protect topsoil while in storage and after it has been redistributed onto the re-graded area. Removed topsoil should be reclaimed technically and its shelf-life period should be ascertained. Soil dumps of different age classes in the area are to be identified and analyzed critically to evaluate the deterioration of soil quality with respect to time, and compared with those of unmined areas. Biological reclamation is essential if the soil is to be stored beyond the shelf-life period.

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Robotics and Intelligent systems in Mining – New wave of technological advances is knocking down the doors

Now in mining, this new wave of technological advances is knocking down the doors of conventional mining methods with improved systems.

It is reported that, Korean mining fields are likely to see a new army of remote-controlled robotic coal-miners in four years time. Australians are also working hard to put Robotics and advanced Intelligent systems for mining operation. It is all about getting people out of hazardous environments and making system safer and productive. Safety, efficiency and better productivity are the key factors driving the trend to automation.

It is expected that, the robots will increase productivity by working around the clock and going deeper, which will reduce the risk of human losses from conventional mining. The robots will not only drill in mines but will up- and offload coal onto conveyers for transportation, with operators outside to control them remotely using a three-dimensional scanner attached at the back of the robots.

Currently, miners often go 2 to 7 kilometers underground to collect coal. Necessity for a mechanized intelligent robotic-miner has been raised as miners can only work four or five hours a day.

Robots will also be doing jobs like laying explosives, going underground after blasting to stabilize a mine roof or mining in areas where it is impossible for humans to work or even survive. Examples of the trend to mining advanced automation include:

a) Tele-operated and automated load-haul-dump trucks that self-navigate through tunnels, clearing the walls by centimeters.

b) The world’s largest “robot”, a 3500 tonne coal dragline featuring automated loading and unloading.

c) A robot device for drilling and bolting mine roofs to stabilize them after blasting.

d) A pilotless burrowing machine for mining in flooded gravels and sands underground, where human operators cannot go.

e) A robotic drilling and blasting device for inducing controlled caving.

Robotic and advanced automation can be helpful in reducing the huge operational costs that exist largely because people are put into hazardous mining environments. These operational costs include making a mine safe and habitable for humans to work. For example, in an underground mine a lot of expenses go into providing good mining environment, cooled air etc. Whereas, machines can operate with lower requirements, reducing the need for expensive infrastructure. Robots must demonstrate efficiency gains or cost savings.

The mining robots and advanced intelligent systems are expected to change the concept of mines and working  conditions as well as improving productivity.

References:

* http://news.mining.com/tag/robotics/

* http://www.koreatimes.co.kr/www/news/biz/2009/08/123_50600.html

* http://www.spacedaily.com/news/robot-00g.html

* http://robotnews.wordpress.com/2006/03/25/robots-in-mining/

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Advanced Communication System Enhances Mine Safety Compliance:

In the interests of mine safety and productivity, it is vital that operators are continuously aware of underground conditions and risk profiles. They must be able to locate and communicate with mine workers at all times – particularly in the event of fires, roof falls or other life-threatening situations. It is equally critical that these communication systems stay active during power outages, fan stoppages or gas accumulations.

In one of the investigations few of common issues regarding communication were identified in a group of mines:  a) The large variety of diverse and proprietary communication systems that were in use at each site.

b) Large numbers of system-generated false and misleading alarms.

c) Time delays in locating and contacting individuals.

d) a cumbersome manual statutory reporting system.

e) Extreme workloads in emergency situations.

Several advanced communication systems for mines have been developed. One of such advanced communication system is Personal Emergency Device (PED). The PED System is an ultra low frequency (ULF) through-the-earth (TTE) communications system used for paging, control and remote blasting. The use of ULF electromagnetic signals enables the PED signal to propagate through several hundreds of metres of rock strata. The signal can therefore be received at any location throughout the mine with an antenna on the surface only or a small underground antenna. The PED system can communicate with the  receivers such as

(a) Personal receiver worn by miners,

(b) Vehicle mounted receiving units,

(c) Remote control of underground equipment,

(d) Radio-based remote and centralised blasting system (for metalliferous mine installations only). Special receivers and exploders receive signals from the PED transmission system (or via the leaky feeder system) to allow the remote initiation of blasts.

References:

http://www.minesite.com.au/

http://www.minesite.com.au/coal_mines_ped_systemc

http://www.csiro.au/science/Underground-communications.html

http://www.mining-technology.com/contractors/communications/mine-site/

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Underground hard rock mining

Underground hard rock mining refers to various underground mining techniques used to excavate hard minerals, mainly those minerals containing metals such as ore containing gold, copper, zinc, nickel and lead, but also involves using the same techniques for excavating ores of gems such as diamonds.

Accessing underground ore can be achieved via a decline (ramp), inclined vertical shaft or adit.

Levels are excavated horizontally off the decline or shaft to access the ore body. Stopes are then excavated perpendicular (or near perpendicular) to the level into the ore.

One of the most important aspects of underground hard rock mining is ventilation. Ventilation is required to clear toxic fumes from blasting and removing exhaust fumes from diesel equipment. In deep hot mines ventilation is also required for cooling the workplace for miners. Ventilation raises are excavated to provide ventilation for the workplaces, and can be modified for use as emergency escape routes. The primary sources of heat in underground hard rock mines are virgin rock temperature, machinery, auto compression, and fissure water. Other small contributing factors are human body heat and blasting.

Some means of support is required in order to maintain the stability of the openings that are excavated.

Stope and retreat vs. stope and fill
Stope and retreat -Using this method, mining is planned to extract rock from the stopes without filling the voids; this allows the wall rocks to cave in to the extracted stope after all the ore has been removed. The stope is then sealed to prevent access.
Stope and fill – Where large bulk ore bodies are to be mined at great depth, or where leaving pillars of ore is uneconomical, the open stope is filled with backfill, which can be a cement and rock mixture, a cement and sand mixture or a cement and tailings mixture. This method is popular as the refilled stopes provide support for the adjacent stopes, allowing total extraction of economic resources.

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Deep-Sea Mining for Massive Sulphides – Recent frontier in Mining Technology

Marine mining has been around for decades. Ocean-floor mining of manganese nodules was in existence since about 1960s. But recently deep-sea mining for copper and gold, contained in a rocky ore deposits called Seafloor Massive Sulphides (SMS), has started.

Deposits are found in underwater volcanic areas around the world and are created by hydrothermal plumes known as ‘black smokers’. When seawater seeps through into the porous seabed, the water is heated down below and is then spurted back up into the ocean through the black smokers. The fluids emitted by these deep-sea vents are rich in metals and high in temperature (around 300-500ºC). When these fluids hit the near-freezing water, the metals precipitate and form chimneys around the plumes. Over time, these chimneys collapse and form the polymetallic sulphide deposits that can are mined today.

Technology in extraction of such deposits is to use Remotely Operated Vehicles (ROVs) to cut and lift sections of the deposit, which are then vacuumed and pumped up a flexible pipeline to the vessel at the surface.

Ref.: http://www.mining-technology.com/features/feature46357/

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Advantages of Underground Mining over Opencast mining

Despite the fact that opencast method of mining is cheaper and safer than underground mining, the distinct advantages of adopting underground method of mining would be:

Underground mining are more environmentally friendly. There is absolutely no damage to the flora and fauna as the following adverse impacts are obviated:

* Noise and vibrations due to blasting as blasting activity is confined to underground location. Impact of Noise & Vibrations is negligible.

* Dust pollution during ore transportation can be totally eliminated as ore transport up to crushers is in confined space. There is no Air pollution.

* Almost 70 % – 80 % of Tailings can be back filled in the mined – out areas underground. Thus, no pollution due to spoil banks as the waste ore can be dumped far away at a permissible pre-determined location.

* There would be minimum activity of “deforestation”. Mining will be underground in confined space. Practically no disturbance of surface land. Rehabilitation & Revegetation is minimal as land degradation is minimal.

* Natural flora and fauna can be maintained and preserved. Thus, disturbance to the Surface Flora & Fauna are negligible.

* Solid waste disposal do not cause any environmental problem as the beneficiation plant can be located away from the forest area. Thus, there is no pollution of nearby water bodies as there is no mine wash-off.

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GPS in Mining:

Global Positioning System (GPS) is useful in Mining including Mine and Ore Body Exploration, Development, Production, Closure, Reclamation etc.

How it works: GPS provides two navigational services: Standard Positioning Service (SPS) and Precise Positioning Service (PPS). SPS is intended for civilian use and PPS for military purposes. SPS uses a single frequency, known as L1, centered at 1575.42 MHz. PPS uses the L2 frequency, centered at 1227.6 MHz. The accuracy of an L1 GPS receiver is roughly 10 to 20 meters horizontally. As might be expected, however, the U.S. military degrades this accuracy to about 100 meters, using a technique called Selective Availability (SA), which is based on misinformation from the satellites. In this way, no one can use GPS against the U.S. with a high degree of precision.

Achieving better accuracies, like those necessary for mining applications, requires the use of a relative positioning technique. One such technique is differential GPS or DGPS. The principle of DGPS is simple. To begin, a GPS receiver is placed at a known, fixed position and allowed to capture GPS satellite signals. Next, the receiver’s computed position is compared to its known position to determine the measurement inaccuracies. Error corrections, known as differential corrections, are then broadcast by radio link to the receivers on the “rovers” (in mining: trucks, shovels, drills, etc.) to fix their calculations and bring accuracy to within meters. DGPS is of such value that the U.S. and Canadian Coast Guards have installed DGPS stations around all major waterways in the U.S. and Canada to aid in ship navigation.

Satellite geometry plays a key role in GPS accuracy, with the best positional readings occurring when the overhead satellites have good spatial distribution instead of being grouped together in a portion of the sky. An ideal geometry of a four-satellite constellation is to have one directly overhead and three low on the horizon and spaced about 120 degrees apart.

Use in Mining Industry: GPS entered the Mining Industry as a fast, and cost-effective instrument for survey. A shifting landscape is the very nature of mining operations; as shovels and dozers remove coal and ore, they reshape the mine’s surface. Real-time GPS allows mining operations to keep on top of these constant changes and provide updated operating instructions to heavy equipment operators. In addition, GPS systems provide a fast and accurate solution for replacing and maintaining control points and calculating the volume of material moved.
Moving mining assets, including dozers, shovels, graders and draglines, are managed and guided using advanced GPS technology. Advanced GPS systems also track and monitor the status and location of dump trucks, providing reports to their heading and velocity as well as the size of the truck’s load. Live GPS is becoming commonplace for monitoring and dispatching haul trucks or drills and for providing grade control on shovels. These data can also be tied to a GIS to monitor the location of all equipment, in real time.

Collision Avoidance: Another possible use of GPS to enhance safety is in collision avoidance. If all mobile vehicles are fitted with GPS and telemetry systems, they can continuously report their position to a central control base. Software at the base can then analyse the data and warn when two vehicles are on a collision course, as is done with civilian air flights in crowded air corridors.

Drill Positioning in Mining by GPS : Modern drill positioning system uses high-precision GPS and on-board Graphics Consoles (GCs) for operator guidance. Each GC displays “virtual” drilling patterns, using predefined blast hole coordinates in the system database. With this information, operators zoom in on hole locations and begin drilling without the use of site markers. When a drill rig is in position to begin drilling, the operator can change the GC display to show drill depth, penetration rate, and depth from bottom of hole. Operators use this information to reduce under- and over-drilling.

Drill & blast design, three-dimensional visualization and enhancement of safety: Mining companies are increasingly looking at global positioning system (GPS) technology, coupled with three-dimensional mine planning and visualization systems, to deliver increased productivity and reduction in operating costs in drilling and blasting operations. Leveraging GPS into drill-and-blast operations requires that a drilling plan be developed and imported into the GPS to guide the operation to a planned and desirable outcome. State-of-the-art mine planning software systems provide the engineer with a three-dimensional environment in which to design and visualize drill-and-blast plans. GPS use in blasting applications is suitable for (a) Establishing preblast survey house locations, (b) Determining blast locations and distances, (c) Establishing spatial relationships, (d) Documenting explosive magazines.

References:

* GPS in Mining: Accuracy (http://www.mmsi.com/gps/accuracy.htm)

* GPS in Mining: http://technology.infomine.com/reviews/GPS/

* Mapping the Mines: The Quest continues: http://www.gisdevelopment.net/application/geology/mineral/geom0013.htm

* Safety Applications for GPS Systems in the Mining Industry:

http://www.qrc.org.au/conference/_dbase_upl/03_spk018_seymour.pdf

* Education-Drilling and Blasting-Docs21 (Blasting application for GPS):

http://www.scribd.com/doc/24714670/Education-Drilling-and-Blasting-Docs21

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Proximity Detection Technologies for Surface Mining Equipment

The lack of visibility near earthmoving equipment resulted in many fatalities in surface mining operations. These accidents were the result of either a piece of equipment striking another vehicle or worker, or the equipment traveling over the edge of an embankment. There is clearly a need to provide better information to equipment operators regarding their surroundings.

A typical proximity warning system consists of a sensor or antenna mounted on the equipment that detects the presence of obstacles and an alarm interface in the cab of the equipment. Some systems also require that other vehicles and personnel on the ground be outfitted with electronic tags that transmit an “I’m here” signal back to the system (e.g., radio signal detection systems or GPS). Many types of proximity warning systems are on the market.

New off-the-shelf systems available for mining equipment include radar and tag-based detection systems. Prototype systems now being developed include a proximity warning system based on the Global Positioning System (GPS) and a computer-assisted stereovision system.

Ref.: http://www.cdc.gov/niosh/mining/pubs/pdfs/ismsp.pdf

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Knowledge Management (KM) in decision making:

The management of knowledge in decision-making as a process is with four parts that comprise a loop.

* Knowledge is created. This happens in the heads of people.

* Knowledge is captured. It is put on paper in a report, entered into a computer system of some kind or simply remembered.

* Knowledge is classified and modified. The classification can be the addition of keywords, or it may be indexing. Modification can add context, background or other things that make it easier to re-use later.

The test of this step is how easily people in the organization will be able to find and use the knowledge when they need it.

* Knowledge is shared. When knowledge is shared and used, the folks who use it modify it. This takes us back to knowledge creation.

Knowledge is the most critical resource for an organization operating in a dynamic environment. Many knowledge management issues center upon such material aspects of control as computers and databases. Other issues, however, deal with the human factor. For those who analyze organizations from a KM perspective, it is the way in which an organization’s actors, both human and computer, process the knowledge resources obtained from shared learning that is most essential to the making of decisions. And, it is the making of decisions that lead to problem solutions, which, in turn, add value to the organization.

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Rugged and Reliable Laptops and Notebooks – Essential for Mining industry:

Laptops and Notebooks used in mining industry must be capable of operating in the most extreme climates in mining operations. This has become a challenge to the computer manufacturing industry to deliver Rugged, Reliable and Robust laptops and notebooks with enhanced performance for field operations.

Today’s equipment providers must carefully take into account weight, shape, functionality, the screen view in bright sunlight and the machine’s ability to ward off chemicals and dust as well, that could hinder electronic operation.

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MINING & CONSTRUCTION EQUIPMENT:

Construction and mining equipment cover a variety of machinery such as hydraulic excavators, wheel loaders, backhoe loaders, bull dozers, dump trucks, tippers, graders, pavers, asphalt drum / wet mix plants, breakers, vibratory compactors, cranes, fork lifts, dozers, off-highway dumpers of various capacity, drills, scrapers, motor graders, rope shovels etc. They perform a variety of functions like preparation of ground, excavation, haulage of material, dumping/laying in specified manner, material handling, road construction etc. These equipments are required for both construction and mining activity.

The technology leaders in the construction equipment sector are: Komatsu, Caterpillar, Hitachi, Terex, Volvo, Case, Ingersoll-Rand, HAMM, Bomag, John Deere, JCB, Poclain, Bitelli, Kobelco, Hyundai and Daewoo.

In the mining sector, the leaders are: Wrigten, Atlas Copco, Liebherr, Joy Mining Machinery, Hitachi, Komatsu, Terex, Ranson & Rappier, Bucyrus Erie and DBT. DBT and Joy Mining Machinery are the two leaders in continuous mining and long wall equipment in the world.

Advances in technology have allowed an increase in haul truck and rope shovel size. For example haul trucks are now being manufactured upto 400 tons capacity. Here the increased machine size has provided an opportunity for increased production.

In the mining industry what has been proven to be productive, safe and available is generally not changed, unless the new technology is more productive, safer and a higher utilization is expected. This is valid for the surface mining technology too. In the open- cast mining industry mechanical mining was more or less limited to soft overburden and pay material (lignite, soft coal). However, in the late 1970s / early 1980s the first cutting systems were introduced to the open cast mining industry which showed a tendency to be able to cut harder materials too. The application of surface miner technology leads to:

• Extracting medium hard minerals by taking advantage of the higher efficiency of continuous excavating.

• Extracting of ‘run of mine’ product in one step which makes at least the primary crushing stage dispensable.

• Eliminates the hazards of blasting and environmental impact arising out of it

• Extracting of valuable minerals in a selective manner for a higher efficiency in the processing plant.

For the user industry the priority that they gave while rating a machine was in the following order:

*Less downtime, *Ease of maintenance, *Power/Fuel consumption, *Efficiency, * Availability of spares parts and servicing and *Eco-friendliness of the machine.

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SOME OF WORLD’S LARGEST EARTHMOVING MACHINES:


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Initiation Systems

1. Safety Fuse:

Uses – To initiate Non-Electrical Detonators or Ordinary Detonators

Ingredients: Black Powder

Properties: Safety fuse is a length of strong, flexible, rope-like product with a black powder core. It is designed to be initiated with a specialty designed fuse lighter or match, burn its length at a predetermined rate, and initiate a non-electric detonator. Safety fuse normally burns at a rate of approximately 35- 45 sec/ft.

Construction: Safety fuse is constructed with various types/quantities of natural and man made fibers and plastic. Safety fuse can usually be identified by its color, wax finish and other manufacturing characteristics observed on its exterior. However, with the use of colored plastics as a final covering, it may be misidentified.

2. Detonators

Initiator is a term that is used in the explosive industry to describe any devise that may be used to start a detonation or deflagration.

Devices that are used to initiate high explosives are called Detonators and devises that start burning or deflagration are called squibs or igniters.

Detonators are used for initiating high explosives and contain small amounts of a sensitive primary explosive. Although they are manufactured to absorb a reasonable amount of shock during handling and transportation, they should not be abused.

In general detonators consist of an ignition charge, intermediate charge, and a base charge. Each charge in the train is selected and used to transition from heat to shock.

A. Non Electrical Detonators (Ordinary Detonators)

(i) Uses – To initiate other explosives, detonating cord and shock tube.

(ii) Ingredients - *Lead Azide, *Lead Styphnate, *PETN, *RDX

(iii) Properties – Non-electrical detonators or fuse caps are thin metal or paper cylindrical shells, open on one end for the insertion of safety fuse, which contain various types of primary and secondary explosives. They are sensitive to heat, shock and crushing and are designed to be initiated with safety fuse or detonating cord. They are normally rated as #8 strength. All detonators of this type are instantaneous and therefore, do not have a delay elements.

(iv) Construction Characteristics:

(a) Shell material - *Aluminium, *Copper, *Gilding metal

(v) Explosives- Contain approximately .65 grams of high explosives.

(vi) Markings- Each shell is marked with a high explosive statement which identifies it as a high explosive and dangerous. Additionally, some of the manufacturers may place their company logo on the shell. The color of the printing is determined by each manufacturer.

(vii) Length- Approximately 2 3/8 inches

(viii) Diameter- .292 inches

B. Electrical Detonators

(i) Uses - To initiate other explosives, detonating cord and shock tube.

(ii) Ingredients:

May contain one or more of the following:

*RDX PETN

*Tetryl Lead Azide

*Lead Styphnate DDNP/Diazo (Diazodinitrophenol)

*Additional proprietary mixes may be utilized for the ignition charge, match and delay elements.

(iii) Properties – Electrical detonators are similar to non-electrical detonators except they are initiated by the application of electrical current through electrical wires. The current causes a bridge wire or match elements to heat/function thereby, causing the ignition charge to explode which in turn, causes a chain reaction to cause the base charge to be initiated. The wires are secured into the detonator by a closure plug, crimped into the shell, which seals the explosive from moisture. In addition to sensitivity from heat, shock and crushing, these products are subject to extraneous electricity due to the presence of electrical wire.

(iv) Types – *Instantaneous, *Short period delay, *Long period delay, *Seismic, *Electronic delay

C. ShockTubes Detonators

(i) Uses – To initiate boosters, detonating cord, other lengths of shock tubes and other explosives. This type of initiation is common to the construction industry, the fire officer will generally find this type of system stored in construction related magazines.

(ii) Ingredients – *HMX and Aluminium Powder

(iii) Properties- Shock tube is a small diameter plastic laminate tube coated with a very thin layer of reactive material at one (1) pound per 100,000 feet of tube. When initiated, shock tube transmits a low energy signal or propagation wave, at approximately 6,500 ft/sec from one point to another. This shock wave is similar to a dust explosion and will propagate through most sharp bends, knots and kinks in the tube. The detonation is sustained by such a small quantity of reactive material, the outer surface of the tube remains intact during and after functioning. Shock tube can be initiated by small shotshell-type primers, detonating cord or detonators.

(iv) Types- *Instantaneous, *Short period delay, *Long period delay, *TrunkLine Delay, *DownTheHole Delay, *Connectors, *In-line delays, *Bunch blocks, *Lead in line

(v) Construction Characteristics – (a) Shell Aluminum, Diameter: .29 inches, Length: 2 3/8 to 4 inches; (b) Tube materials, Construction – Polyethylene, Surylyn; (c) Explosives- HMX, Aluminium powder; (d) Length- 3 to 2500 feet, Diameter: .12 inches.

D. Programmable Electronic Detonators

Refer: Programmable Electronic Detonator System

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India’s present Underground Coal Mining scenario : “A story of a prolonged-neglected hungry child, suddenly asked to perform with high proficiency”!!

Shri G.L.Tandon (padmabhushan) has rightly mentioned about the sheer neglect done to Indian underground coal mining sector for past several decades, and thereby restricting severely the development & production of coal from underground mines in India.

There are host of problems that underground mines in India face. Two major coalfields in India namely Jharia and Rnigunj coal filds have large number of seams and have high density of population. These two facts together have created major mining problems. High density of population with facilities like roads, power lines etc., has prevented large scale opencast mines of shallow depth seams and resulted in standing pillars of underground mining that could not be extracted. Because of that, many areas are affected by underground coal fire. Similarly, many areas of standing pillars are waterlogged.

Another difficulty being faced by Indian coal mining industry is inefficient extraction of thick coal seams by underground method. This problem exists not only in Jharia and Ranigunj coalfields but in other coalfields as well. A good portion of Indian coal reserve is in the form of thick seams. Many areas of thick seam have been developed in two or even more sections. A great lot of difficulties are being faced in extracting standing pillars of such seams. In fact, Indian coal industry is yet to adopt proper underground methods / technology in extracting thick coal seams in a large scale. In such a bleak scenario, improvements have to be worked out by infusing efficient technology suitable for a particular coal seam / mine, by which pace of production is raised considerably, wastage of coal left in the goaf is kept minimum and greater safety is maintained.

However, CIL Chairman’s endeavour to increase coal production from its underground mines is highly commendable. Everybody, those who are involved in such mining activities, should take the challenges to adopt to toughness, riskier and dangerous underground mining system and at the same time, higher authorities should support them wholeheartedly. Moreover, technological inputs of highest order should be incorporated into the system from very beginning, for making it safer and productive.

We all know, Underground coal mining operations are environmentally friendlier and prone to less dilution than coal obtained from Openpit coal mining operations.

In this respect, I feel, suggestion of forming separate entity for “Underground Coal Mining operation”, should be given due importance.

In fact, the system should work as an organization and it must have a culture of trust. Risk taking must be condoned, because ideas are paramount, and not all ideas end up working. It must not only share successes, but failures as well, because sharing both are critical to learning. It is absolutely critical for the organization to buy in and encourage workers to share information.

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35 thoughts on “HOME

  1. Sir,

    I gone through your paper and fully agree with fact to increase the production from underground will be difficult task.

    Very informative articles thanks for sharing

    Regards

    Neeraj

  2. it provides vital information on rock blasting and innovative technologies for the future mining industry. i really thanks for this article .it will definitely help in my future projects and PhD thesis. GREAT WORK ………..

  3. To increase the rate of production from Indian UG coal mines is quite possible if at there is sufficient exposure and FDI specific deregulation is allowed. Logwall is very famous and highly efficient method of extraction, but the Indian specific problem being the thick seams. French BG method is also widely used in the thick seams of Singereni Coalaries on an experimental basis and quite safely being carried even today. But the issue with these western/modern methods to be used in India is the inability of the Indian labors to understand/learn the necessary operational know how’s to be implemented in the field on a long term basis. Hope this will soon end and private players are soon allowed to use the best practices necessary for production enhancement and Quality improvement.


    Varun

  4. Your article really interesting, I really liked the article that you created and this is very useful information for us. Thank you for providing very valuable information for us, you want to share.

    Regards

    Clark Miners

  5. Very informative article.Can you share something about blast design for Production in Vertical Crater Retreat Method.

    regards,

    Basant

  6. Sir I have gone through all the publishing,and I believe all I have seen here. Am a citizen of nigeria, a student of auchipolytechnic edo state, mineral resource engineering nd1. I want to no if there is any help I can get from this organization academically,because I want to be a mining engineer.

  7. Dear Sir,
    I read this very complete article of yours. I wonder if you know of any study relating blasts in open mining with the dust the explosions naturally produce.
    Thanks in advance
    acp

  8. Dear sir,
    thanks a lot sir, too much imp information today i had received.for First class exam point of view u r blog is PATHDARSHAK in current mining scenario.
    arun

  9. Dear sir
    I was glued while reading these papers, and it will be very kind of you if I could get some more information regarding EXPLOSIVE-IMPEDANCE-MATCHING.
    Thank you.
    Manish Sammuk
    I.S.M, Dhanbad.

    • Impedance Matching or, more accurately, Impedance Approximating –

      The concept of impedance matching has been a fundamental principle in electronics for many years. While it differs in some respects from electronics, the concept of impedance matching can be applied to the process of transferring energy from the explosive into the rock.

      The impedance of an explosive is represented by its shock energy production rate. The impedance of rock is represented by the rate at which it can accept the transfer of shock energy.

      Very roughly (for conceptual purposes), Explosive impedance would equate to the density of the explosive multiplied by the detonation velocity of the explosion.

      Rock impedance would equate to the density of the rock multiplied by the velocity of sound in rock.

      Since the impedance of a given piece of rock is fixed, any attempt at impedance matching would obviously have to entail the selection of an explosive that would more closely match the impedance of the rock. Because calculated impedance values in rock are usually far higher and have a much greater range than those calculated for conventional explosives, a better name for the concept of impedance matching might be impedance approximating
      .
      To take advantage of the concept, the blaster would select an explosive with a lower impedance value (lower density, lower velocity) when attempting to blast rock with a lower impedance value (lower density, lower velocity) and, conversely select a higher impedance explosive to blast rock with a higher impedance value.

      While impedance approximating will assist you in achieving better blasting results, the structure of the rock (joint systems, etc.) will play a very important part and will usually have a greater effect on blast results. Study the rock structure carefully. Consider it in your blast designs and then select your explosives to match the rock.

  10. Sir Your article really interesting, I really liked the
    article that you created and this is very useful
    information for us. Thank you for providing
    very valuable information .

  11. dear sir
    you are giving us a really valuable information in detail and you really helping us to save our time by bringing all mining information under one roof.
    I’m glad to you sir if you can send the information about the maximum and minimum ratios of rock impedance to explosive impedance for better blasting processes.
    thank you sir,
    subbu avasarala,
    B.Tech Mining engineering
    ISM Dhanbad

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