Cost effectiveness of open-pit hard rock Ore Mining

Cost effectiveness in open-pit hard rock Ore Mining

Cost effectiveness of open-pit hard rock Ore Mining depends on Explosives used in terms of Energy / VOD, Pit-slope angle and framing strategy for fragmentation *** Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/ Abstract Extensive in-situ testing has shown that blast fragmentation influences the performance of downstream processes in a mine, and as a consequence, the profit of the whole operation can be greatly improved through optimised fragmentation.

Other unit operations like excavation, crushing and grinding can all be assisted by altering the blast-induced fragmentation. Therefore, it is necessary to couple all the parameters, namely selection of explosives in terms of VOD, rock properties and surface blast design for an efficient blasting. Fragmentation is one of the most important concepts of Explosives Engineering. The efficiency of these unit operations is directly related to the size distribution of muckpile. Therefore, reliable evaluation of fragmentation is a critical mining problem. Apart, cost effectiveness in open-pit mines is the result of maximizing pit-slope angle and reduction in blast damage and ore dilution which results in increased volume of final products as well.

Slope stability and increase in pit-angle depend on blast performance and adoption of controlled blasting to mitigate the adverse effects. Pre-splitting of production blast is the way for achieving steeper slope angle in open pit ore mining. One of the objectives in pre-split blasting is to control over break, so that the final pit wall slopes are kept stable and competent. To arrive such a optimum levels, an overall knowledge of the process and operational aspects of rock blasting techniques are essential.

1. Introduction - Drilling and blasting is one of the main operations in open-pit mining, and its performance has a major impact on the overall economy of the mine. Blasting by design results from a large number of factors, all of which need to be brought under control in order to achieve the right result. These include the choice of drillrig and tools, the layout of the holes, the explosive, and the skill of the operators.

Explosives are used for rock breakage in mining and construction industry. In mining the main objective is to break largest possible quantity of rock with optimum fragmentation and minimum cost. In construction industry explosives are used for construction of tunnels, caverns, dams, foundation excavations etc. Here the objective of blasting is to have fast progress leaving behind smooth and stable rock.

------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining To understand the principles of rock blasting, it is necessary to start with the rock fragmentation process that follows the detonation of the explosives in a drillhole. The explosion is a very rapid combustion, in which the energy contained in the explosives is released in the form of heat and gas pressure.

The geology and rock condition frequently has more effect on the fragmentation than does the explosive used in the blast. The properties that influence the result of the blast are compressive strength, tensile strength, density, propagation velocity, hardness and structure. In general, rock has a tensile strength which is 8 to 10 times lower than the compressive strength. The tensile strength has to be exceeded during the blast, otherwise the rock will not break. High rock density requires more explosives to achieve the displacement. The propagation velocity varies with different kinds of rock, and is reduced by cracks and fault zones. Hard, homogeneous rocks, with high propagation velocity, are best fragmented by an explosive having high velocity of detonation (VOD). Thus, selection of explosives is one of the most important criteria in getting proper performance. It has to compatible with the rock formation.

In fact, surface blast design is always in a constant state of adjustment. It involves manipulation of numerous variables that influence the eventual outcome of using explosives to break rock. Through proper adjustment of these variables the blst designer can create the most favourable conditions for efficient use of explosives energy. In addition, efficient management of explosive energy and on-site conditions will have a direct influence on the economic of blasting, the rate of productivity through better fragmentation and reduction of vibration, airblast, flyrock and overbreak.

Extensive in-situ testings has shown that blast fragmentation influences the performance of downstream processes in a mine, and as a consequence, the profit of the whole operation can be greatly improved through optimised fragmentation. Other unit operations like excavation, crushing and grinding can all be assisted by altering the blastinduced fragmentation.

Therefore, it is necessary to couple all the parameters, namely explosive, rock properties and surface blast design for an efficient blasting. Fragmentation is one of the most important concepts of Explosives Engineering. The efficiency of these unit operations is directly related to the size distribution of muckpile. Therefore, reliable evaluation of fragmentation is a critical mining problem.

Apart from above, cost effectiveness in open-pit mines is the result of maximising pitslope angle and reduction in blast damage and ore dilution which results in increased volume of final products as well.

2. 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 ------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining 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 Fig. 1.

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.

Fig - 1 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. a. Rock breakage by Detonation and Interaction of explosive energy with rock – There are three sources of generation of fragments in mines: (a) Fragments formed by new fractures created by detonating explosive charge, (b) In-situ blocks that have simply been liberated from the rock mass without further breakage and (c) Fragments formed by extending the in-situ fractures in combination with new fractures.

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.2).

------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining

Fig. 2 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.3). 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 face 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.

------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining 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.3). The extent of this zone is 20 to 50 times the radius of blast hole (Siskind and Furnanti, 1974).

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.

Fig - 3 b. Cratering Theory - 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.

------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining 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: B E = -------Q1 /3 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. c. Energy factor of Explosives – The purpose of the application of explosives during blasting is to perform useful work. The work may be the fragmentation of rock or ore, throw of muck-pile etc. Energy factor in an explosive is the amount of explosive energy required to fragment a given quantity of rock. Thermo-chemical energy can be used as an index of effectiveness of an explosive to break rock.

Kilocalories (Q) Energy factor (EF) = -------------------------Quantity of rock EF is expressed in Kilocalories/Cum or Ton. It is always a better practice to design blasts using energy factor. As the explosives of various types have different energies ranging from 600 Kcals/kg to 1200 Kcals/kg , it is possible to match the required energy levels varying from 100 Kcals/Ton to 300 Kcals/ton. While arriving at the energy factor for a particular rock type, extensive trials are necessary over a considerably long period. This experience can be gainfully used in blast designs.

3. Role of VOD in selection of explosives for effective performance - The performance of a blast depends on various factors such as blast geometry, pattern of drill holes, sequence of firing, initiation system used and performance of explosives. Important o properties of explosives which influence the performance are density, strength, VOD, sensitivity and cohesiveness. Among all these VOD has a major role in selection of explosives. Besides reducing the drilling cost and the ground vibration, use of proper explosives improves fragmentation and stability of the rockmass.

------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining VOD of an explosive can be defined as the velocity at which the detonation wave passes through the explosive column. The VOD of commercial explosives vary from 2500 m/s to 5000 m/s.

As per the rock type the selection of explosives on the basis of VOD generally takes place. It has been found that, maximum explosive energy is transferred to the rock when the impedance of explosives matches with the impedance of the rock to be blasted. The energy transfer is influenced by coupling factor and impedance factor.

(Zex - Zr)2 σ = 1 - ------------------(Zex + Zr)2 σ is Impedance Factor; Zr is impedance of the rock; Zex is impedance of explosives.

Impedance ‘Zr’ is product of rock density ‘ρr’ and seismic velocity in the rock ‘Vr’; i.e, Zr = Vr * ρr in kg-m2 /s. Similarly, ‘Zex’ is product of explosive density ‘ρex’ and VOD of the explosive ‘Vex’; i.e, Zex = Vex * ρex in kg-m2 /s.

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 (Fig. 4).

Fig - 4 ------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining An explosive with low VOD releases energy at a slower rate and large proportion of this energy is in the form of Heave or Gas energy. Such explosives are suitable for soft and fractured rock. Explosives with high VOD have higher Shock energy component, thus are suitable for tough, hard and massive rock.

Base Nitro-glycerine

Type Dynamite geletine

VOD (m/s) 5500 - 4500

Ammonium Nitrate

ANFO

2500

Water

Slurry / Emulsion

4000 – 3000 watergel 5000 Emulsion Range depend on storage time

Feature Highly adaptable cartridged.

Excellent in smaller holes Low cost, high safety, easy to pour or blow.

No water resistance, contains 5-6% fuel oil Basically ANFO made water resistant gel.

Stable oil/water emulsion – heavy ANFO. Packaged or pumpable

4. Selection of explosives and drilling for minimizing drilling cost – Drilling is a costly and time consuming operation. It can be reduced either by using large diameter holes or by using high VOD explosives or by combining both. With high VOD explosives the extent of transition zone increases. This permits expanded pattern, thereby reducing the total meterage of drilling, hence reduction of drilling cost. It has been observed that, shifting from ANFO explosive to bulk emulsion explosive, there is substantial benefit in reduction of drilling cost in hard rock open pit ore mining.

Similarly, using higher diameter blast-holes, the pattern as well as bench height can increased, thereby reducing overall cost and improving efficiency and productivity.

5. Fragmentation Strategy and maintaining optimum height & pit-slope angle in open-pit mining geometry for maximum cost effectiveness – Traditionally, focusing on the drilling cost parameter and productivity only, the predominant method in open pit mining is large hole drilling using hole sizes in the range of about 250 mm. No doubt this implies lower cost for drilling, ignoring the expense of excess waste, more explosives and less controllable fragmentation.

------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining

Fig.5 In fact, a major difference between open pit mining and quarries is the geological conditions and the demand characteristics on the blasted material. Whereas quarries deliver the majority of rock via the crushing and screening plant in various size fractions, the open pit mine attempts to deliver the ore as pure as possible via crushers to the dressing plant, consisting of mills, separators, and/or flotation, and/or biochemical systems, and finally to smelters, in order to convert minerals to metals. Maintaining pit slope angles that are as steep as possible is of vital importance to the reduction of stripping (mining of waste rock), which will in turn have direct consequences on the economy of the mining operation. Design of the final pit limit is thus governed not only by the ore grade distribution and the production costs, but also by the overall rock mass strength, stability, controlled blasting techniques adopted, type of drilling machines (vertical or inclined) used etc.

In hard rock open-pit ore mine, without jeopardizing slope stability, it is of prime importance to keep the pit slope angle as steep as possible, maintaining excavated waste at a minimum. The demands on fragmentation of the waste, as it does not pass through the crushing/dressing system, are simple. It should merely suit the loading and trucking equipment used for subsequent removal to the waste dump. On the other hand, good fragmentation of the blasted ore will make great savings in the total cost of the mineral dressing process.

6. Using pre-splitting for making bigger and steeper bench to save waste extraction In general, in order to reduce over all mining cost, mines are adopting high capacity of excavators thereby increasing bench height, use of larger diameter blast holes and more powerful explosives. These changes however resulted in high-energy concentration in the blast area which results in severe back break problems for final pit walls. If back break is ------------------------------------------------------------------------------------------------------Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

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Cost effectiveness in open-pit hard rock Ore Mining not controlled, it ultimately decreases the overall slope angle, with major economic consequences such as decreased recoverable ore reserves and increased ore to waste ratios. Greater amount of face loose rock will be produced and wider berms will require to be left to ensure the safety of the pit walls. There must be trade off between the money saved by using the larger equipments and blasts, and money spent to maintain the pit walls. The best approach is to control the effects of blasting so that the inherent strength of the walls is not destroyed. The purpose of pre-splitting is that to isolate the blasting area from the surrounding rock mass by forming an artificial plane to limit gas and stress wave penetration into the remaining nearby rock formation.

The theory of pre-splitting is that when shock waves from simultaneously detonating charges in adjoining blast holes collide, tension occurs in the rock, forming a crack in the web between the holes. For that reason it is important that charges are detonated simultaneously or as close as possible.

Blasting will not only break the rock that is planned to be excavated, but will also cause damage to the slopes that form the boundaries of the pit. The extent of this overbreak is mainly dependent on the size of the individual charge and its proximity. A common means of minimizing overbreak is to use smaller diameter holes, making provision for restricted blasting in the zone next to the planned bench slope. A typical drilling pattern applied in connection with pre-split blasting, to achieve increased slope stability with reduced back break shown in Fig.6.

In order to achieve better result number of experimental trials is required to carryout before establishment of full-proof system. Different combinations of blast pattern, explosives, drilling diameter, angle etc., are to be tried. For example, varying the spacing, hole angle, charge per square metre, use of gas bags, bottom initiation, cartridge diameter, stand off distance between pre split and buffer row, number of buffer rows, hole diameter of buffer rows, different drill patterns, different blast designs, powder factor, number of rows in a blast, blast size etc. trials to be carried out.

------------------------------------------------------------------------------------------------------- 10 Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

Cost effectiveness in open-pit hard rock Ore Mining

Fig.6 It should be remembered during trials that, not only the dynamic tensile strength of rock but also the overall Rock Mass Rating, the joint sets and foliation planes do also plays an important role in success for pre-split blasting. Stability at steeper angle and higher bench height depends much on success of pre-split blast. The type of explosive used plays a great role, and its quantity should be gradually reduced till an optimum powder factor is obtained. Gaining experience by analyzing various results obtained during trials is the most important factor in achieving subsequent satisfactory pre-split results.

Fig.7 For effective pre-splitting, another technical point to be taken into consideration that, there needs to be a “stand-off� distance between the pre-split plane and the buffer (or nearest production) blast-holes. Where ever this stand-off distance is too small, the production blast generates break backs beyond the pre-split plane. Where the stand-off ------------------------------------------------------------------------------------------------------- 11 Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

Cost effectiveness in open-pit hard rock Ore Mining distance is too large, it may be difficult to expose the pre-split plane. Sometime, there may be a possibility of leaving layer of unbroken rock, adhering to the pre-split plane.

Therefore, thorough study of the rockmass and its changing pattern is called for before deciding the blast pattern, quantity of explosives to be used and delay sequence. If introduction of stab holes between inclined pre-split holes and buffer are needed, these are to be provided (Fig.7 and Fig.8).

Fig.8 Slope stability, increase in bench height and increase in pit-angle depend on blast performance and efficiency of controlled blasting adopted to mitigate the adverse effects.

Blasting adverse effects such as overbreak, ground vibration etc., are directly proportional to the loading density of explosives and borehole pressure exerted by the explosives. Again, borehole pressure is function of VOD of explosives used (P = 2.5 * 10-6 * Ď * V2 ; where, P is borehole pressure in kilobar, Ď is density of explosives and V is VOD of explosives in m/s). Thus control of adverse effects, to some extent, depend on selection of explosives as per VOD. Conclusion - Success of pre-splitting depends on number of factors, such as blast pattern, explosive used, drilling diameter, angle etc. It should be realized that, there is tremendous scope of saving in rock excavation, by just making the pit slopes one degree steeper. Again, there is substantial amount of savings in waste extraction by increasing the pit as well; with suitable combinations of earth moving machineries employed.

Moreover, strategy of fragmentation, which is to be implemented in the mines, should be very clear to everybody and accordingly blasts are to be designed. Fragmentation of waste rock to be kept maximum as per capacity of earthmoving machineries deployed, ------------------------------------------------------------------------------------------------------- 12 Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

Cost effectiveness in open-pit hard rock Ore Mining whereas, the fragmentation of ore has to be kept low to increase crusher and mill throughput.

Therefore, substantial savings can be made if proper drilling, selection of explosives, blasting and fragmentation strategy is followed in an optimum way.

References: * Langefors, U. Kihlström, B. 1963, The modern technique of rock blasting. Almqvist & Wiksell/Gebergs Förlag, Stockholm, Sweden * Siskind,D.E., Fumanti,R.R., (1974), “blast produced Fractures in Lithuania Granite”, USBM, RI 7901 (pp. 38). * “Explosives and Rock Blasting”, Atlas powder Co., USA. * Hagan, T.N. 1973, Rock Breakage by Explosives. Proc. Nat. Symp. on Rock Frag. Aust.

Geomech. Soc., pp 1-7. * Persson, A., Holmberg, R. and Lee, J. 1994, Rock Blasting and Explosives Engineering , CRC Press, Inc. * Rustan, A. 1990, Burden, spacing and borehole diameter at rock blasting. Proc 3rd Int Symp on Rock Fragmentation by Blasting, Brisbane, pp 303-310. * Scott, A. (Ed) Cocker, A. Djordjevic, N. Higgins, M. La Rosa, D. Sarma, KS. Wedmair, R. 1996, Open Pit Blast Design-Analysis and Optimization. Julius Kruttschnitt Mineral Research Center, University of Queensland. * Thornton, D. Kanchibotla, S. and Brunton, I. 2001b, Modelling the impact of rockmass and blast design variation on blast fragmentation. Explo 2001, AusIMM, Hunter Valley, NSW, pp197-205. * Hall, J., and Brunton, I. 2001, Critical comparison of Julius Kruttschnitt Mineral Research Centre (JKMRC) blast fragmentation models. Explo 2001, AusIMM, Hunter Valley, NSW, pp207-212. * Jaeger, J.C. and Cook, N.G.W. 1979, Fundamentals of Rock Mechanics, 3rd edition, Chapman and Hall, London. * Kuznetsov, V.M. 1973, The mean diameter of fragments formed by blasting rock, Soviet Mining Science, Vol. 9 No. 2. * Sjöberg, J. 1999, Analysis of Large Scale Rock Slopes. Luleå University of Technology.

Doctoral Thesis 1999:01. * Winzer, S.R. Ritter, A.P. 1980, The role of stress waves and discontinuities in rock fragmentation: a study of fragmentation in large limestone blocks. Proc. 21st Symp. on Rock Mech., I.S.R.M., pp 362-370. * Chiappetta, R.F. 2001. The importance of pre-splitting and field controls to maintain stable high walls, eliminate coal damage and over break. Proc. 10th Hightech Seminar on State of the Art Blasting Technology, Instrumentation and Explosives Application, GI-48, Nashville, Tennesse, USA, July 22–26. * Firouzadj, A., Farsangi, M.A.E., Mansouri, H. & Esfahani, S.K. 2006. Application of controlled blasting (Pre-splitting) in Sarcheshmeh copper mine. Proc. 8th Int. Symp. on Rock Fragmentation by Blasting, Santiago, Chile, 7–11 May, pp. 383–387. Santiago: Editec.

------------------------------------------------------------------------------------------------------- 13 Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/

Cost effectiveness in open-pit hard rock Ore Mining * Olofsson, S.O. 1998. Applied explosives technology for construction and mining: 183– 186. Rotterdam: Balkema. * Bhandari, S., 1997, Engineering rock blasting operations, A.A.Balkema, Rotterdam. * Singh, P.K., Roy, M.P., Joshi, A., Joshi, V.P., 2009, Controlled blasting (pre-splitting) at an open-pit mine in India, Proc. Int. symposium on “Rock fragmentation by blasting”, Fragblast9, Granada (Spain), pp 481-489. * Partha Das Sharma; ‘Controlled Blasting Techniques – Means to mitigate adverse impact of blasting’; Procc. of 2nd Asian Mining Congress, organized by MGMI at Kolkata (India) dt. 17th – 19th January 2008 (pp: 286 – 295).

----------------------------------------------------------------------------------------------------Author’s Bio-data: Partha Das Sharma is Graduate (B.Tech – Hons.) in Mining Engineering from IIT, Kharagpur, India (1979) and was associated with number of mining and explosives organizations, namely MOIL, BALCO, Century Cement, Anil Chemicals, VBC Industries, Mah. Explosives etc., before joining the present organization, Solar Group of Explosives Industries at Nagpur (India), few years ago.

Author has presented number of technical papers in many of the seminars and journals on varied topics like Overburden side casting by blasting, Blast induced Ground Vibration and its control, Tunnel blasting, Drilling & blasting in metalliferous underground mines, Controlled blasting techniques, Development of Non-primary explosive detonators (NPED), Hot hole blasting, Signature hole blast analysis with Electronic detonator etc.

Author’s Published Books: 1. "Acid mine drainage (AMD) and It's control", Lambert Academic Publishing, Germany, (ISBN 978-3-8383-5522-1).

2. “Mining and Blasting Techniques”, LAP Lambert Academic Publishing, Germany, (ISBN 978-3-8383-7439-0).

3. “Mining Operations”, LAP Lambert Academic Publishing, Germany, (ISBN: 978-3-8383-8172-5).

Currently, author has following useful blogs on Web: • http://miningandblasting.wordpress.com/ • http://saferenvironment.wordpress.com • http://www.environmentengineering.blogspot.com • www.coalandfuel.blogspot.com Author can be contacted at E-mail: sharmapd1@gmail.com, sharmapd1@rediffmail.com, ------------------------------------------------------------------------------------------------------------------Disclaimer: Views expressed in the article are solely of the author’s own and do not necessarily belong to any of the Company.

------------------------------------------------------------------------------------------------------- 14 Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blog/Website: http://miningandblasting.wordpress.com/