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

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					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: sharmapd1@gmail.com,
       Blog/Website: http://miningandblasting.wordpress.com/

                                           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.

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
          Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering,                   1
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Blast Fragmentation Appraisal
Means to Improve Cost-Effectiveness in Mines
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.

 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.

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;
         Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering,                     2
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Blast Fragmentation Appraisal
Means to Improve Cost-Effectiveness in Mines
* 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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Blast Fragmentation Appraisal
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 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.

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.

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Means to Improve Cost-Effectiveness in Mines
* 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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Blast Fragmentation Appraisal
Means to Improve Cost-Effectiveness in Mines
on fragmentation results had been studied by many researchers. These variables are
powder factor, drilling pattern, borehole diameter, delay timing, and drilling inaccuracy.

 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.

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.



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Blast Fragmentation Appraisal
Means to Improve Cost-Effectiveness in Mines
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

 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.

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.

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




                                          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;

         Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering,                     9
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Blast Fragmentation Appraisal
Means to Improve Cost-Effectiveness in Mines
* 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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Blast Fragmentation Appraisal
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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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Blast Fragmentation Appraisal
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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.


         Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering,                       12
                         E.mail: sharmapd1@gmail.com,
              Blog/Website: http://miningandblasting.wordpress.com/
Blast Fragmentation Appraisal
Means to Improve Cost-Effectiveness in Mines
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
Blasting, Lulea, Sweden, August 1990, pp. 469 –494.

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Motion Modelling with Comparison to Bench Blast Field Data”, Proceedings of the 4th
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and Blasting Research, ISEE, U.S.A., 1997, pp.125 –134.

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RI 5849, 1961, 14 p.

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4583, 1950, 31 p.

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.A., 1987, pp. 72 –79.

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418 –425.


         Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering,                     13
                         E.mail: sharmapd1@gmail.com,
              Blog/Website: http://miningandblasting.wordpress.com/
Blast Fragmentation Appraisal
Means to Improve Cost-Effectiveness in Mines
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.

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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.

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

				
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Description: 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.