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

Blast Fragmentation Appraisal

Means to Improve Cost-Effectiveness in Mines

Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering,

E.mail: [email protected],

Blog/Website: http://miningandblasting.wordpress.com/

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Means to Improve Cost-Effectiveness in Mines ***




1. Introduction - A blasted rock muckpile and the fragment sizes within it are very

important for the mining industry since they affect the downstream processes from

hauling to grinding. The size distribution of the blasted muckpile can be predicted by a

variety of semi empirical models which are based on blast design parameters, such as

burden, spacing, drillhole diameter, bench height and explosives consumption. Despite

their few limitations, models are commonly used, since they provide reasonable trends to

evaluate changes in blast design parameters.

The optimization of the final rock fragment/product size on a cost basis must result in the

minimum total cost that the drilling and blasting design parameters can generate.

Generally, the cost of drilling is the sum of two major components, capital and

operational cost, while the blasting cost consists of mostly the cost of explosives, blasting

accessories and labour.

It is common for mine operators to seek the optimum drilling and blasting cost. However,

when no fragmentation specifications are provided, this is a vague target. Similarly, it is

quite common for mine operators to be concerned with fragmentation only when

difficulties in drilling and loading are encountered, or when a large amount of oversize is

produced, resulting in a general loss of productivity in the crusher and/or secondary

Abstract

Fragmentation is a major concern of any blasting operation. Information on the degree

and size distribution of fragments within a blasted rock mass is essential for efficient

rock loading and crushing operations. Estimation of blast fragmentation are generally

done by considering four basic variables, i.e. rock properties, explosive properties,

drilling pattern and bench geometry. Apart, in reality, because of the non-uniform

burden along the bench height, the actual powder factor in the front row of holes

could differ significantly from the one estimated assuming uniform burden. Ignoring

this fact may result in a poor fit of the existing fragmentation models for the actual

data.

Drilling and blasting are seen as sub-systems of size reducing operations in mining.

To have better design parameters for economical excavation of mineral production

and fragmentation, the comminution and fragmentation operations need to be studied

and optimized independently, as well as together, to create optimized use of energy

and cost-effective operation. Thus, fragmentation is the basic concern in rock blasting

and serves as the main measure of blasting effectiveness.






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blasting. It is desirable to have a uniform fragment size distribution, avoiding both fines

and oversizes. It is very important that blast pattern can be quickly and accurately

analyzed before actual blast. Any mining operators can minimize total production costs

per ton of rock blasted. This requires an evaluation of the component costs, which include

drilling, blasting, loading, hauling and crushing costs.

Blast fragmentation is mostly sent to the milling section for further reduction of size for

metallurgical/chemical processing plants. In most cases the material from the crusher is

sent for grinding to reduce it to the required size for processing. Clearly it is important to

be able to accurately calculate the passing size from the mine, which should be at least

80% feed size for the mill. This can be related to the blast design parameters, which in

turn can be used to calculate cost at each drill-hole diameter assisting in the selection of a

drill machine suitable to drill a required diameter size drill-hole with a minimum cost of

production.

2. Mechanism of rock breakage by blasting - Blasting theory is one of the most

interesting, challenging, and controversial areas of the explosives engineering. It

encompasses many areas in the science of chemistry, physics, thermodynamics, shock

wave interactions, and rock mechanics. In broad terms, rock breakage by explosives

involves the action of an explosive and the response on the surrounding rock mass within

the realms of energy, time and mass. In spite of the tremendous amount of research

conducted in the last few decades, no single blasting theory has been developed and

accepted that adequately explains the mechanisms of rock breakage in all blasting

conditions and material types. There is as yet no consistent and widely applicable theory

of blasting, but only a number of limited theories, many of which are empirical in nature

and based on ideal situations. Generally, reflected theory is considered due to its

simplicity and ease of application.

Rock fracture resulting from explosion process of explosives load in drill holes depend

on the number of free faces, the burden, the hole placement and rock geometry, the

physical properties and loading density of the explosive, the type of stemming, the rock

structure and mechanical strength, and other factors. Final fragmentation in a bench

blasting operation can be attributed to a combination of:

* Crushing of the rock immediately around the explosive cavity;

* Initial radial fracturing due to tensile tangential stress component in the outgoing stress

wave;

Bond, in 1961, presented his third law of comminution, formulating a mathematical

equation to calculate the amount of work done on the 80% passing particle feed size to

convert it into 80% passing particle product size, using a constant, called the Work

Index, to balance the equation. Bond’s Work Index is defined as the energy in Kwh

per short ton required to reduce the material from theoretically infinite feed size to

80% passing an opening size of 100 microns. This law is still widely used and to date

no other law has proven to be better.






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* Secondary radial fractures formed at the surface, propagating inward, due to enhanced

tangential stress accompanying free surface displacement;

* Extension of the initial radial fractures by reflected radial tensile strain at oblique

angles to the surface;

* Joining of inward propagating radial fractures with initially created outward radial

fractures;

* Tangential fractures formed at the surface, propagating parallel to the free surface;

* Tensile separation and shear of rock at places of weakness in the rock mass;

* Separation of the rock due to reflected radial tensile strain;

* Fracture and acceleration of fragments by strain energy release;

* Further fracture and acceleration of broken rock by late expanding gases; and

* Pre- existing discontinuities in the rock mass.

Most of the rock breakage in a blast occurs at a free face as a result of spalling, which

occurs when a compressive wave is reflected at a free boundary. The slabs, which are

spalled from the rock edge, are formed in a succession of increasing thickness, where the

number of slabs depends on the amplitude and duration of the stress wave.

The shock wave generated by the blast travels to the free surface from which it reflects. If

the tensile strength is low, compared to the amplitude of the tensile portion of the wave,

the rock face will spall. The spalled rock then travel away from the remaining rock with a

certain velocity. This is obviously a contribution to the overall ‘heave’ of burden rock.

3. Extent of blast damage zone - The prediction and observation of the nature and extent

of the damage produced in the surrounding rock when an explosive charge detonates in a

borehole is of major practical significance for engineered rock excavation. The radius of

the damage zone formed when a cylindrical charge detonates in a rock mass is one of the

most important parameters required in the development of a scientifically based method

for designing blast patterns. The process taking place in the rock surrounding a charge is

so complex that an exact mathematical description is presently impossible. The damage

mechanisms change as the distance from the explosion increases.

4. Factors of Blast Design - Preliminary blast design parameters are based on rock mass-

explosive-geometry combinations, which are later adjusted on the basis of field feedback

using that design. The primary requisites for any blasting round are that it ensures

optimum results for existing operating conditions, possesses adequate flexibility, and is

relatively simple to employ. It is important that the relative arrangement of blast-holes

within a round be properly balanced to take advantage of the energy released by the

explosives and the specific properties of the materials being blasted. There are also

environmental and operational factors peculiar to each mine that will limit the choice of

blasting patterns. The design of any blasting plan depends on the two types of variables;

uncontrollable variables or factors such as geology, rock characteristics, regulations or

specifications as well as the distance to the nearest structures, and controllable variables

or factors. The blast design must provide adequate fragmentation, to ensure that loading,

haulage, and subsequent disposal or processing is accomplished at the lowest cost.






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Further to the cost, the design of any blast must encompass the fundamental concepts of

an ideal blast design and have the flexibility to be modified when necessary to account

for local geologic conditions. The controllable and uncontrollable factors are used in the

blasting and costing models wherever necessary.

4.1. Uncontrollable factors - Uncontrollable parameters concerning blast design are the

rock mass properties and the geological structure. These have to be considered in the

blast design.

a. Properties of rock - A natural composite material, rock is basically neither

homogeneous nor isotropic. Inhomogeneity in rock is frequently discernible from its

fabric, which includes voids, inclusions and grain boundaries. Anisotropy is due to the

directionally preferred orientations of the mineral constituents, modifications in the

changing environments and characteristic of geological history, which may alter its

behaviour and properties. The intrinsic environmental factors that influence drilling are

geologic conditions, state of stress, and the internal structure of rock, which affect its

resistance to penetration.

The following parameters affect rock behaviour to drilling:

* Geology of the deposit: Lithology, chemical composition, rock types.

For a given rock type, geologic structure, and firing sequence, an increase in the

degree of fragmentation may be achieved by

(a) Increasing the consumed quantity of a given explosive,

(b) Changing to an explosive having greater energy content per unit hole volume

(higher energy content/ density), or

(c) Combinations of both.

For blasting case (a) the associated drilling cost would increase if the explosive

quantity were to be increased by simply drilling the same diameter drill holes but on a

tighter pattern. Thus there would be more drill holes required to blast a given volume.

If larger diameter drill were substituted and the increased hole volume achieved in this

way then the rate of increase or decrease would depend upon the comparative drilling

cost per metre of hole.

For case (b), assuming that the same hole diameter and pattern are used, the drilling

cost would remain constant independent of the fragmentation.

For case (c) the drilling cost could remain constant, increase or decrease depending

upon the situation.

Therefore, it is essential in establishing a methodology for blast fragmentation

prediction and to develop a fairly satisfactory engineering model for fragmentation

size prediction based on the methodology established in order to achieve cost-

effectiveness. Thereafter, verify the model by comparing field data with predicted

values.






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* Rock strength and properties: Mechanical properties, chemical and physical

properties.

* Structural geology: Presence of fractures, fissures, folds and faults.

b. Presence of water - Depending on the source and quantity, it may be an

uncontrollable or a controllable factor. These factors also influence the blast design

parameters and the fragmentation produced; thus their effects to blasting need to be

quantified.

c. Rock factor - An attempt to quantify the effect of rock parameters on fragmentation

was made by Cunningham (1987), who used Lilly’s (1986) “blastability index A”, and

incorporated it in his popular Kuz Ram model (Cunningham, 1983). He discussed that

every assessment of rock for blasting should at least take into account the density,

mechanical strength, elastic properties and fractures. He defined the rock factor ‘A’ as;

A = 0.06*(RMD + JF + RDI + HF) ,

where ‘RMD’ is the mass description, ‘JF’ is the joint factor, ‘RDI’ is the rock density

influence and ‘HF’ is the hardness factor.

4.2. Controllable factors - For the purposes of blast design, the controllable parameters

are classified in the following groups:

a- Geometric: Diameter, charge length, burden, spacing etc. Geometric parameters are

actually influenced by uncontrollable and controllable factors, which are also design

parameters and can be grouped as follows:

(i) Diameter and Depth of Drillhole.

(ii) Inclination and Subdrilling Depth of Drillhole.

(iii) Height and Material of Stemming.

(iv) Bench Height.

(v) Spacing to Burden Ratio.

(vi) Blast Size, Direction and Configuration.

(vii) Initiating Sequence and System.

(viii) Buffers and Free Faces.

(ix) Explosive Type, Energy and Loading Method.

(x) Powder Factor q =Q/V where Q is the total quantity of explosive per borehole and V

is the total volume of rock blasted.

b- Physicochemical or pertaining to explosives: Types of explosives, strength, energy,

priming systems, etc.

c- Time: Delay timing and initiation sequence.

5. Effect of Controllable Blast Parameters on Fragmentation - Prediction of the rock

fragmentation distribution resulting from a given bench blast operation is not an easy

task, since theoretical developments of rock breakage are hindered by the numerous

variables influencing the phenomenon. More than twenty factors appear to affect

fragmentation in a blast. The effect of interaction between several blast design variables






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on fragmentation results had been studied by many researchers. These variables are

powder factor, drilling pattern, borehole diameter, delay timing, and drilling inaccuracy.

Fragmentation results described by the mean fragment size alone are inadequate and a

full description of the entire size range is needed. Increasing inaccuracy in hole position

results in a significant decrease of degree of uniformity of the blasted material. Greater

borehole diameters or, in other words, higher specific consumption of explosives gives

better and more uniform fragmentation. When the amount of explosive per hole is such

that the radius of affected rock mass from the explosion is small, drilling misalignment

not only gives non- uniform fragments but also bad fragmentation.

The analysis of the effect of controllable blast parameters on fragmentation using the

literature review lead to the following conclusions:

1. For the effect of powder factor on fragmentation, it was found:

* the predicted behavior of characteristic fragment size (63.9% passing) with powder

factor match well with that predicted by Kuznetsov’s equation (Kuznetsov, 1973;

Cunningham, 1983, 1987; Lownds, 1983).

* a decrease of the uniformity of fragmentation was found with decreasing powder factor

(Lownds, 1983).

2. The drilling pattern has the following effect on fragmentation:

* staggered pattern gives lower characteristic fragment size compared to the square

pattern for the same powder factor, because of the better distribution of explosives in the

rock mass in the former case.

* staggered pattern gives more uniform distribution.

3. A greater borehole diameter produces a better and more uniform fragmentation for a

given blast pattern.

An important parameter, often linked to the distribution of explosive energy in the

blast is the drill-hole diameter. It controls the distribution of energy in the blast and

thus it affects fragmentation. Large diameters are often associated with expansion of

drilling patterns; however large holes intersect fewer in-situ blocks of rock, resulting

in more oversize, especially in the case of jointed rock. Typically the drill-hole

diameter is changed depending upon the rock or drill machine type. Similarly,

changes in the bench height when a new loading machine is introduced or for any

other reason, affect changes on all dependent parameters or on the blast muck pile

size mix.

Modifications in a drill-hole diameter or a bench height or a product size tend to

change all other relevant blast design parameters. The effect of the changes of

blasting parameters, when the fragmentation output is specified, is to be studied. A

costing model must be designed to calculate the cost of drilling and blasting once

fragmentation targets are provided. Finally the effect of blast-hole diameter on the

drilling and blasting cost must be analyzed.






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4. Inaccuracy in drilling had a negative effect on uniformity of fragmentation. However,

no effect on the characteristic fragment size was observed, except in the case of low

usage of explosives where the characteristic fragment size was found to increase as the

drilling deviation was increased.

The following parameters are related to muckpile uniformity.

(i) Distribution of explosive in the blast (burden, spacing to burden ratio, borehole

diameter, collar, subgrade, bench height)

(ii) Firing accuracy of detonators used

(iii) Timing of detonators used

(iv) In situ fragmentation due to geological discontinuities

6. Effect of Discontinuities on Rock Fragmentation By Blasting - Rock properties are

the uncontrollable variables in blast design. Blast performance is influenced by geologic

structure and rock strength. In almost every mining practice, the rocks are far from

homogeneous. There are joints, bedding planes, mud or soft seams, which have a major

effect on blasting performance. These are defined as planes of weakness within a rock

mass along which there has been no visible movement. There will be a difference in

transmission of the stress waves through the joints depending on whether the joint is

tight, open or filled. Tight joints do not affect the transmission of stress waves whereas

the open and filled joints introduce an acoustic impendance mismatch and reflect the

stress waves. If the reflected wave is sufficiently strong, internal spalling takes place. The

radial cracks, which the strain wave would have formed in a continuous rock, are

prematurely interrupted by the joint.

Many investigators have studied the effect of discontinuities on rock breakage induced by

blasting. A brief review of their results is presented below:

* Fourney et al., (1983) has found in his model scale experiments a joint initiated

fragmentation mechanism. For a layered medium this mechanism of joint initiated

cracking yields a much smaller average fragment size than would be obtained in a

homogeneous media. This reduction in fragment size is at least 1.5 times.

Generally, an occasional problem lies in the realistic assessment of fines. It is felt

that these can be generated both by the equipment loading the rock, and through

weak binding material between mineral grains in addition to the intensive crushing

of rock around the boreholes during blasting. It is interesting to note that fine

materials have varied utilization. Sometimes fines are considered for further

metallurgical and chemical processing, while at other times fines are rejected and

become waste. To address the coarse as well as the fine portion of the muckpile, The

major portion of the muckpile is the result of tensile failure while the fine size

fragments in the muckpile are because of shear and compressive stresses

surrounding the borehole. Prediction of fragmentation by blasting is often based on

the assumptions that a single-distribution of pre-existing discontinuities is present

within a blasted rock volume and that the underlying mechanism of failure is tensile

failure.






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* Da Gama (1983) found in full- scale bench blasts that less energy is required to

fragment a discontinuous rock than a homogeneous rock and used the Bond’s third law of

comminution to estimate this energy reduction.

* Harries (1983) in full-scale bench blasts found that any increase in the mean spacing

between joints and/or bedding planes partings demands that a greater degree of new

breakage is created in a blast. An increase in the degree of fissuring usually encourages

the use of greater burdens, blast-hole spacing and collar (or stemming) length and

correspondingly lower energy factors.

* Ash (1973) stated that better fragmentation occurs when drill holes are oriented along

lines perpendicular to the most prominent joint face of the rock mass. Large fragments

result from those lines of drill holes parallel to that joint face.

7. Study of Rock Fragmentation by Blasting - Empirical models which can be used to

study fragmentation by blasting was given by Cunningham (1983). His model

incorporates Kuznetsov’s work (1973) on relating explosive energy, hole size and rock

characteristics to mean fragment size, and the Rosin- Rammler curves for assessing

fragment size distribution. This approach is used extensively by AECI, the major South-

African industrial group, for designing blast and, providing the chose of values for the

rock is correct, gives a fairly good match to data obtained in actual tests.

Harries and Hengst (1977) constructed a digital simulation model to study rock

fragmentation due to blasting. This model was the basic for further models that can be

used in routine blasting work such as the SABREX program (Scientific Approach to

Blasting Rock by Explosives), and Lownd’s FRAG model (1983). In these models

various assumptions were made for the propagation of cracks and these were

programmed into a simulation model of the blasting area.

BLASPA has been used by Favreau (1983) and others for modeling blasting for many

years. Recently, Favreau (1993) has described some of the aspects of the swell module

used in the model and the results obtained. This model can be only applied to description

of particle motion during a blast.

The spherical element computer program DMC_Blast, developed by Preece in 1989, has

been modified a few times. A new version of that program (Preece et al., 1997) performs

coupled gas flow and rock motion simulations in a bench blasting environment. Several

different equations of state are included for modeling the behavior of the explosives.

The equation of state for explosive gases allows modeling of many different explosives.

The program muckpile contours are in good agreement with those observed in the field.

Generally, the basic steps involved in choosing proper blast parameters that ensure

desired rock fragmentation for creating an engineering model are depicted in Fig-1.






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Fig - 1

The engineering model generally can be used to:

* Predict the effect of blasthole size, explosives selection, and many other parameters on

the resulting fragmentation distribution;

* Predict the effect of a bench face irregularities on the fragmentation distribution;






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* Design a blasting technique to provide a specified results, for example, a reduced

fragmentation size range;

* Determine the effect of discontinuities in the rock mass on blast fragmentation

distribution.

8. Verification of the Engineering Model made – As discussed, there has been

considerable research conducted in rock fragmentation prediction. Most of the published

data does not have enough input information about bench face angle, rock properties,

explosives types, and, in the same cases, drilling pattern. Of course, the missing input

data can be substituted by using average values. But such substitutions will cause some

prediction errors. Also, there are no published literature that have the complete

information including: 1) angle of bench face; 2) angle of breakage; and 3) size

distribution.

As a result, in general, new field data are used to verify the model. The effect of varying

blast designs is analyzed with respect to the predicted and actual size distributions in a

surface mine. Image analysis method is the most popular method used to determine the

actual size distribution by using the digital camera and image–processing programs such

as “Wip-Frag”, “Split–Desktop” etc.

Visual observations of muckpiles immediately following the blasting are widely used by

mine operators to arrive at an approximation. These observations are qualitative.

However, for normal everyday purposes image analysis method has the following

advantages over other forms of visual evaluation methods such as sieving and boulder

counting:

* it is simple to use;

* it gives a good approximation of the size distribution for a given blast;

* measurements in the field are quick and less intrusive in the production process;

* the images obtained form a good record of the blast; and

* the cost of equipment is affordable.

9. Image analysis technique and sampling - The use of image analysis techniques for

fragmentation analysis requires careful consideration of the three stages in the process:

sampling, image acquisition and image analysis itself. Sampling concerns the taking of

images that represent the blasted material being analyzed. Image acquisition concerns

taking of images which are of sufficient quality for the intended analysis process. Image

analysis refers to the measurement of size distribution of fragments identified in the

image. First the image is captured by the analysis computer and stored as an array of

picture points (pixels) of varying brightness. Then image processing may be used to

modify it to enable the computer to identify each individual fragment. The results are

then converted from a two- dimensional to a three dimensional parameter by empirical or

stereological techniques.

At any given scale, image analysis can measure fragments within a size range determined

by the minimum resolvable size and the maximum visible size. The size range is

dependent on the image analysis technique. The minimum sizes are comparable but for a






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large fragments the surface texture may cause automatic methods to detect false edges to

produce a group of small fragments. Obviously, the greater the number of images, the

nearer the result will be to the truth.

Blasted material can be sampled either before digging (the muckpile surface), during

digging (at the face), or while in haul trucks. The first two methods can lead to errors due

to subjective judgment of the material to be photographed, since more material can be

seen than can be sampled. The use of haul truck sampling is advantageous as the camera

location can be fixed in a position and can be automated, although the effect of material

sorting during loading needs to be taking into account. Environmental conditions affect

the quality of images. These conditions, such as poor lighting, shadows and dust, are

difficult to control in surface mines and may cause poor quality images.

10. Conclusion – Under certain favorable geologic conditions (relatively short distance

of muckpiles from the faces, and fairly high efficiency of explosive excavation) the

cheapest method of moving the overburden is the blast casting method. In this mining

method the degree of fragmentation achieved is an important economic factor. If the

degree of fragmentation obtained from blast casting is to be predicted, a special crack

analysis model, which takes into account further enhancement of fragmentation due to

collision of fragments and their falling on a hard surface, must be included.

A high-speed camera should be used to monitor the full scale blasts in order to study the

mechanisms of crack initiation, propagation, and interaction in bench blasting. A high-

speed camera can also be used to determine the throwing direction and the velocity

distribution in each region. It will help to relate the theoretical burden velocity with the

velocity distribution inside the burden, and the throwing direction of the broken mass to

determine the muckpile profile.

A series of full-scale blast tests should be conducted to study the effect of the density of

discontinuities on the mean fragment size and uniformity of fragmentation. Furthermore,

field oriented studies may be taken up with high-speed photography techniques for a

better understanding of the effect of discontinuities on rock fragmentation by blasting. By

this way the understanding of fragmentation can be improved in the near future, for

example effective selection of the face orientation, burden, spacing, etc. required with

respect to weakness planes present in the rock mass. Since the size distribution is the

major determining factor in loading and hauling operations, the predicted average

fragment size can be used to combine the entire operation together. The improved

computer program will provide more help to blast designers and mine operators. Also, it

can be used for cost analysis of changing the blasting pattern or explosive type.

References: Langefors, U., and Kihlstrom, B., “The Modern Technique of Rock Blasting”, Wiley, New York,

1963, pp. 405 –411.

Bond, F. C. 1961. “Crushing and Grinding Calculations”. Allis-Chalmers Manufacturing

Company, Milwaukee, Wisconsin.






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Kuznetsov, V. M., “The Mean Diameter of Fragments Formed by Blasting Rock”, Soviet Mining

Science (in Russian), Vol. 9, Moskow, 1973, pp. 144 –148.

Lilly, P. A., “An Empirical Method of Assessing Rock Mass Blastability”, Proceedings, Large

Open Pit Mining Conference (J. R. Davidson, ed.), AIMM, Parkville, Victoria, Canada, October

1986, pp. 89 –92.

Cunningham, C. V. B., “The Kuz–Ram Model for Prediction of Fragmentation from

Blasting”, Proceedings, First International Symposium on Rock Fragmentation by Blasting,

Lulea, Sweden, August 1983, pp. 439 –453.

Cunningham, C. V. B., “Fragmentation Estimations and the Kuz–Ram Model–Four Years on”,

Second International Symposium on Rock Fragmentation by Blasting, Keystone, Colorado,

U.S.A., August 1987, pp. 475 –487.

Da Gama, D., “Use of Communution Theory to Predict Fragmentation of Jointed Rock Masses

Subjected to Blasting”, Proceedings, First International Symposium on Rock Fragmentation by

Blasting, Lulea, Sweden, August 1983, pp. 565 –579.

Fadeenkov, N. M., “Applicability of the Rosin–Rammler Law to the Analysis of the Grain–Size

Composition of a Heap of Blasted Rock”, Soviet Mining Science, Volume 10, No.2, Moskow,

1975, pp. 685 –688.

Hustrulid, W., and Kuchta, M., “Open Pit Mine Planning and Design, Volume 1 Fundamentals”,

Balkema, Rotterdam, 1998, pp. 254 –255.

Hustrulid, W., “Blasting Principles for Open Pit Mining: Theoretical Foundations, Volume 2”,

Balkema, Rotterdam, 1999, pp. 980-992.

Azarkovich, A. E., “Influence of Natural Jointing of Ledge Rock on the Radius of Crack

Formation During an Explosion”, Soviet Mining Science, Volume 17, No. 1, Moskow, 1981, pp.

29 –38.

Ash, R.L, “The Influence of Geological Discontinuities on Rock Blasting”, Ph.D.

Dissertation, University of Minnesota, Minneapolis, 1973, 289p.

Worsey, P., Rustan, A., Line, N. S., “New Method to Test the Rock Breaking Properties of

Explosives in Full Scale”, Second Symposium on Rock Fragmentation by Blasting, Keystone,

Colorado, U. S. A., 1987, pp. 485 –487.

Shapurin, A. V., and Kutuzov, B., “Blast Round Design for Open Pit Mines", Manual

for the Explosives and Mining Engineering Students, Department of Explosives Engineering,

Moskow State Mining Institute, Moskow, 1990, p.55.

Bhandari, S., “Changes in Fragmentation Process with Blasting Conditions”, Proceedings, 5th

Symposium on Rock Fragmentation by Blasting, Montreal, 1996, pp. 301 – 309.

Bhandari, S., “Engineering Rock Blasting Operations”, A. A. Balkema, Rotterdam, 1997,

pp. 191 –195.






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Hjelmberg, H., “Some Ideas on How to Improve Calculations of the Size Fragment Size

Distribution in Bench Blasting”, Proceedings, First Symposium on Rock Fragmentation By


Preece, D. S., Burchell, S. L., Scovira, D. S., “Coupled Explosive Gas Flow and Rock

Motion Modelling with Comparison to Bench Blast Field Data”, Proceedings of the 4th

International Symposium on Rock Fragmentation by Blasting, Fragblast-4 ( H .P Rossmanith,

ed.), Vienna, Austria, July 1993, pp. 239 –245.

Preece, D.S., Tidman, J. P., Chung, S. H., “Expanded Rock Blasting Modelling Capabilities Of

DMC_BLAST, Including Buffer Blasting”, Proceedings, 13th Annual Symposium on Explosives

and Blasting Research, ISEE, U.S.A., 1997, pp.125 –134.

Preece, D. S., and Khudsen, S. D., “Blasting Induced Rock Motion Modelling Including Gas

Pressure Effect”, 24th U.S. Oil Shale Symposium (J. H. Bary, ed.), Quarterly Colorado School Of

Mines, Volume 83, No. 4, Golden, Colorado, U. S. A., 1991, pp. 13- 19.

Higgings, M., BoBo, T., Girder, K., Kemeny, J., and Seppala, V., “Integrated Software

Tools and Methodology for Optimization of Blast Fragmentation”, International Society of

Explosives Engineers Annual Conference, 1999, 7 p.

Fourney, L. W., Barker, B. D., and Holloway, C. D., “Fragmentation in Jointed Rock

Material”, Proceedings, First International Symposium on Rock Fragmentation by


Porter, D. D., “Use of Rock Fragmentation to Evaluate Explosive in Blasting”, Mining Congress

Journal, Volume 60, No. 1, 1974, pp. 41 – 43.

Petkof, B., Atchison, T.C., Duvall, W. I., “Photographic Observation of Quarry Blasting”, USBM,

RI 5849, 1961, 14 p.

Obert, L., Duvall, W. I., “Generation and Agitation of Strain Waves in Rock – Part I”, USBM,RI

4583, 1950, 31 p.

Nie, S. L., and Rustan, A., “Technique and Procedures in Analysing Fragmentation After Blasting

by Photographic Method”, Proceedings, Second International Symposium on Rock

Fragmentation by Blasting, Keystone, Colorado, U. S. A., 1987, pp. 102- 113.

Mohanty, B., “Strength of Rock under Strain Rate Loading Conditions Applicable to Blasting”,

Proceedings, Second Symposium on Rock Fragmentation by Blasting, Keystone, Colorado, U. S

.A., 1987, pp. 72 –79.

McHugh, S., “Computational Simulations of Dynamically Induced Fracture and Fragmentation”,

Proceedings, First International Symposium on Rock Fragmentation by Blasting, Lulea, Sweden,

August 1983, pp. 407 –418.

Margolin, L. G., and Adams, T. F., “Numerical Simulation of Fracture”, Proceedings, First

International Symposium on Rock Fragmentation by Blasting, Lulea, Sweden, August 1983, pp.

418 –425.






14

McDermott, C., Hunter, G. L., and Miles, N. J., “The Application of Image Analysis to the

Measurement of Blast Fragmentation”, Proceedings, Symposium Mining-Future Concepts,

Nottingham University, Marylebone Press, Manchester, 1989, pp. 103- 108.

MacKenzie, A. S., “Optimum Blasting”, Proceedings of the 28th Annual Minnesota Mining

Symposium, Duluth, 1967, pp. 181 –188.

Maerz, N. H., Franklin, J. A., Rothenburg, L., and Coursen, D. L., “Measurement of Rock

Fragmentation by Digital Photoanalysis”, Proceedings, Fifth International Congress

International Society of Rock Mechanics, 1986, pp. 687- 682.

Lownds, C. M., “Computer Modelling of Fragmentation from an Array of Shotholes”,

Proceedings, First International Symposium on Rock Fragmentation By Blasting, Lulea, Sweden,

August 1983, pp. 407 –418.

Blair, B. E., “Use of High–Speed Camera in Blasting Studies”, USBM, RI 5584, 1960, 32p.

----------------------------------------------------------------------------------------------------- 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: [email protected], [email protected],

------------------------------------------------------------------------------------------------------------------- Disclaimer: Views expressed in the article are solely of the author’s own and do not necessarily

belong to any of the Company.

***

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

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