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MINISTRY OF EDUCATION AND TRAINING
UNIVERSiTY OF MINING AND GEOLOGY





nguyen dinh AN



RESEARCH ON DETERMINING POWDER FACTOR
TO ENSURE A PROPER FRAGMENT SIZE FOR
LIMESTONE QUARRIES IN VIETNAM



Branch: Mining Engineering
Code: 62520603


SUMMARY OF DOCTORAL DISSERTATION





ha noi - 2014
The dissertation was completed at: Surface Mining Department,
Mining Faculty, University of Mining and Geology

Science Instructor:
1. GS.TS. Nhu Van Bach, University of Mining and Geology
2. TS. Nguyen Dang Te, VINACONEX

Reviewer 1: TSKH Nguyen Thanh Tuan - Vietnam mining science
and technology association

Reviewer 2: TS Nguyen Phu Vu - Vietnam mining science and
technology association

Reviewer 3: TS Nguyen Sy Hoi - Vietnam mining science and
technology association

The dissertation will be defended before the Council of Doctoral
dissertation assessment help at Hanoi University of Mining and
Geology at …………… on………………2014






The dissertation can be found at the National Library in Hanoi or
Library University of Mining and Geology
1

INTRODUCTION

1. Urgency of subject

In mining industry in general and open pit mining in particular,
blasting is an important which influences directly loading, haulage
and milling phase.
Nowadays, there are many achievements in research of blasting
theory and blasting material in mining industry, especially of blasting
parameters for improving rock fragmentation efficiency.
Powder factor is very important in blasting. Explosive cost used
to break a volume unit of rock according to requirement and blasting
mission is called as powder factor. Powder factor is a blasting
parameter which depends on physical and mechanical characteristic
of blasting, size requirement of rock fragmentation, explosive type,
blasting technology, other blasting parameters and so on.
Some equations of powder factor have been applied in Vietnam.
However, they are not close to practice in mines due to factors
influencing powder factor are determined not accurately.
According to mining experiences from overseas and
disadvantages of blasting in open pit mines, especially in quarries in
Vietnam, research on determining powder factor to ensure a proper
degree of rock fragmentation for some quarries in Vietnam is very
urgent. Annually, there are millions m
3
of rock blasted and hence, if
good calculation of powder factor can be done to decrease 1÷2%, the
amount of explosive used will be reduced considerably. Research
results will assist mining companies being more active in blasting and
improving their business and production which contributes to ensure
investment efficiency for new technology and more safety for
humans and surrounding environment.
Therefore, the PhD dissertation “Research on determining
powder factor to ensure a proper fragmentation size for

limestone quarries in Vietnam’’ is very urgent, satisfying practical
demands in mining industry in Vietnam.


2

2. Research purposes of dissertation
Based on explosives materials made in Vietnam and theory,
research works in domestic and from overseas as well as
experimental results of research on relations of factors affecting
powder factor. I propose a method to determination of reasonable
powder factor to ensure a proper fragmentation size for limestone
quarries in Vietnam, which used for some limestone quarries in
Vietnam to improve economic and technical standards of blasting.
3. Object and research scope
- Research object is determining powder factor to ensure a proper
degree of rock fragmentation for quarries, mainly in Vietnam.
- Research scope is blasting practice in quarries in Vietnam.
4. Research content
- Research on blasting technology in mining, powder factor and
other blasting parameters.
- Research on factors affecting powder factor.
- Research on relation between powder factor and explosive
degree and degree of rock fragmentation.
- Research on determining powder factor to ensure a proper
degree of rock fragmentation for quarries in Vietnam.
5. Research methods
- General method, analytical and comparative method, inheritance
method, statistical and graphic method.
- Theoretical and experimental method.

6. Scientific and real significance
Powder factor is an important blasting parameter affecting and
relating closely to other blasting parameters. Accurate determination
of blasting parameters plays the decisive role in quality and efficiency
of blasting in mines.
Research result is creating a method to determine powder factor
based on a scientific foundation and a relation between powder factor
and impact coefficients, ensuring it is employed favorably in quarry
mining.


3

Research result can be applied in quarries in Vietnam and
guarantee efficiency and reduction of impacts on environment.
7. Theoretical points to defend
1. Powder factor is a basic one which plays an important role in
blasting in quarries. Impact coefficients of powder factor are divided
into two groups: group of variables and group of coefficients.
2. Technical powder factor (q
cn
) determined according to
required degree of rock fragmentation (d
tb
) and degree of crack (d
max
)
is a foundation to determine powder factor for any blasting
conditions. Relation between q
cn

và d
tb
is linear.
3. Reasonable powder factor in quarry mining is determined by
technical powder factor (q
cn
) combining theory with experiment based
on qualitative relation between powder factor and two impact groups.
8. New points of dissertation
1. Determining powder factor for quarries using explosive made
in Vietnam, millisecond delay non-electric blasting technique and
based on required degree of rock fragmentation in quarry mining.
2. Based on relation between powder factor and impact
coefficients, classification of the impact coefficients is made by
dividing them into two groups which are better in determining an
optimal powder factor.
3. Function of powder factor is made according to classification
of groups of impact coefficients.
4. The software for designing blasting report is build from a
proper powder factor.
8. Composition of the dissertation
The dissertation includes more than 145 pages and lots of tables,
graphs, figures and references in domestic and from overseas.
Generally, except introduction and conclusion part, the dissertation
composites the following chapters:
Chapter 1 - Overview of researches of powder factor and other
blasting parameters.
Chapter 2 - Research on impact factors of powder factor.

4

Chapter 3 - Relation between powder factor and explosive degree
and degree of rock fragmentation
Chapter 4 - Research on determining powder factor to ensure a
proper degree of rock fragmentation in some quarries in Vietnam.
9. Publications
Based on research trend shown in the dissertation, I have 15
research works which are published in journal of mining industry and
domestic and international conferences.
CHAPTER 1: OVERVIEW OF RESEARCHES OF POWDER
FACTOR AND OTHER BLASTING PARAMETERS
1.1. OVERVIEW OF BLASTING TECHNOLOGY IN MINING
Valuable deposits are often extracted by open pit or underground
method in which mostly rock with hardness degree of f = 6÷14 and
70% of valuable materials are necessary to break into desired size.
Currently, rock fragmentation methods are done mainly by
blasting using boreholes and small holes.
1.2. ROLES OF POWDER FACTOR IN MINING
One of the most fundamental standards used in evaluating
efficiency of rock fragmentation is size of blasted rock or degree of
rock fragmentation. This degree depends on mining equipment
dimension (bucket capacity, haulage method, and milling). Whereas,
powder factor is a key parameter to determine the degree of rock
fragment.
1.3 SOME DIFINITIONS OF POWDER FACTORS
1.3.1 Calculated powder factor, q
This powder factor is used to calculate and for initial design or
carrying out initial blasting in specific conditions according to
requirements of blasting. Some other authors treat it like powder

factor.
1.3.2 Practical powder factor, q
th

This term helps companies improve their management as well as
it is a real value which is used in blasting under the same condition.
The reason is that practical powder factor only is calculated after
finishing blasting and loading works.


5

1.3.3. Powder factor for creating standard explosion crater, q
c

Powder factor for creating standard explosion crater is the costs
pending in breaking a bank volume unit of rock to create a standard
explosion crater.
1.3.4 Standard powder factor, q
0

The quality of blasting is evaluated by the size of rock
fragmentation. Hence, standard powder factor is the adequate cost
spending in breaking a bank volume unit of rock to get required size
of rock fragmentation (in standard explosion condition).
1.3.5 Reasonable powder factor, q
hl

Reasonable powder factor is the adequate cost spending in a
volume unit of rock so that the total cost of all technological phases is

minimized.
1.4. OVERVIEW OF BLASTING PARAMETERS IN SURFACE MINING
There are two types of blasting parameters in open pit mining
including: parameters of drilling pattern and parameters of explosive
charge.
1.5. OVERVIEW OF RESEARCHES ON POWDER FACTOR
Relevant researches on powder factor includes as followings:
- Method of determining powder factor according to required size
of rock fragmentation (Kuznetsov, B.N Kutuzov).
- Method of determining powder factor according to power of
explosive (I.P.Oxanhit and P.X. Mirônov).
- Method of determining powder factor according to standard
powder factor (V.V. Rjevxki).
- Method of determining powder factor according to the rule of
size distribution within blasted rock heap.
1.6. EVALUATION OF RESEARCHES ON POWDER FACTOR
1.6.1. Comments about researches published on powder factor
1. All researches admit that powder factor is a fundamental
parameter which affects directly the quality of rock fragmentation
and cost of mining product.
2. Almost researches evaluate accurately about factors in
qualitative aspect which affects the determination of value of powder


6

factor. Impact coefficients can be divided into some groups as
followings:
Group 1: Factors characterize environment of blasting such as
physical and mechanical properties of rock, degree of hardness,

degree of crack, rock density,
Group 2: Factors of explosive are used as a standard. Researches
can be choosing Ammonite N
o
6 or ANFO to be a standard explosive
depending on explosive production industry, blasting condition and
rock properties in each country.
Group 3: Researches also are interested in parameters of blasting
pattern, especially in diameter of charge, d. Other parameters are
admitted only in qualitative aspect and only mollifying with a
rational factor in quantitative aspect depending on specific blasting
conditions or just according to experimental values.
Group 4: In case of control blasting methods such as millisecond
delay blasting, decked charge blasting, high bench blasting and
blasting in high pressure, researches often choose an experimental
factor to evaluate.
Research method and equation foundation go through three steps
as followings:
Step 1: Doing a research on the theory of relation between
powder factor and its impact coefficients.
Step 2: Carrying out experiments in lab or industrial experiments
to determine some quantitative values.
Step 3: Establishing a specific relation between powder factor and
relevant coefficients. Besides, factors having a little or no impact will
be are experimental values.
1.6.2. Problems existing in researches on powder factor
a. Researches do not concern fully features of power properties
of explosive in selecting explosives which are used as a standard in
calculating.
b. The introduction of millisecond delay blasting method (1934 ÷

1935) and non - electric facility (1970 ÷ 1973) has been brought a big
efficiency in open pit mining. Millisecond delay non-electric blasting


7

using modern firing facilities is better than others because of some
advantages as followings :
- Being able to control the degree of rock fragmentation due to
increase impact time of explosion and crushed control zone on rock.
- Being able to widen drilling pattern (due to create a large free
face) and simultaneously, ensure the quality of fragmentation. Hence,
it contributes to decrease drilling cost.
- Reducing power factor whereas improving quality of
fragmentation.
- Being able to increase blasting scale and control ground
vibration.
- Millisecond delay non-electric blasting improves quality of
fragmentation and reduces harmful effects on environment
(especially ground vibration). However, scientific foundation of
efficiency of rock fragmentation of millisecond delay non-electric
blasting is researched not comprehensively in Vietnam.
c. Rock broken by blasting is a complex environment in which it
is non-identical and isotropic. Explosion process occurs very quickly
so that determining stress state of each point is very difficult. Using
equivalent materials to model explosion samples and experimental
factors to converse it into practical environment in blasting are often
make a large error.
d. Equations established are often complicated or contain lots of
experimental factors which reduce ability to apply in practice.

e. In general, all researches in domestic and from overseas affirm
that the degree of rock fragmentation (shown in diameter of grain
size) influences considerably power factor. At the moment, there is
no research which solves deeply and completely this problem and
fixes with practical situation in quarries in Vietnam. Hence, it is able
to propose some problems to research next as followings:
Establishing a method to determine a proper powder factor in
quarries in Vietnam is based on: Using millisecond delay non-electric
blasting method with explosive made in Vietnam (ANFO); required
degree of rock fragmentation in quarries.


8

CHAPTER 2: RESEARCH ON FACTORS AFFECTING
POWDER FACTOR
2.1. REQUIREMENTS OF BLASTING IN QUARRY
- Grain size of rock fragmentation must be uniform and oversize
rock must be very few.
- Dimension of blasted rock heap (height, width) must fix with
loading and haulage equipments in order to ensure production and
safety for them and being suitable with parameters of mining method.
- Bench floor must be smooth and limits postpulse and improves
capacity factor of drillhole.
- Blasting activity must ensure strict safety for humans, houses
and buildings under the effect of ground vibration, air blast and flying
rock.
2.2. FACTORS AFFECTING POWDER FACTOR
- Factors are featured for environment which blast activity takes
place.

- Economic and technical factors include blasting parameters,
type of explosive being used, and firing method.
2.3. COMMENTS AND EVALUATION OF RELATION BETWEEN
POWDER FACTOR AND IMPACT COEFFICIENTS
Coefficients affecting powder factor can be divided into two
groups:
Group of variables includes coefficients that affect directly and
change powder factor continuously. They are:
+ Chemical and physical properties of rock include hardness
factor f and degree of crack.
+ Required degree of rock fragment that is grain size of blasted
heap rock and characterized by average size of rock.
Group of coefficients includes factors which influence powder
factor in a certain level, depending on explosion condition, as
followings:
+ Type of explosive
+ Method of firing control
+ Technology and technique of carrying out blasting.


9

CHAPTER 3: RELATION BETWEEN POWDER FACTOR AND
ROCK BLASTABILITY AND DEGREE OF ROCK
FRAGMENTATION
3.1. RELATION BETWEEN POWDER FACTOR AND DEGREE OF
EXPLOSION
Blasting considers rock as a main object to impact. Degree of
explosion characterizes how difficult to fire explosive are and is
determined by powder factor under a standard condition. The larger

powder factor is, the higher degree of explosion is and vice versa.
3.2. ROCK CLASSIFICATION IN MINING
Classification of rock plays an important role in mining. It is
based on selection of drilling machine, method of firing, mining
production norm and cost of blasting material.
3.2.1. Foundation of rock classification
Foundation of rock classification according to degree of
explosion is powder factor q
o
. Based on this factor, grain size of
blasted rock heap distributes as a line on graph.
Method of determination of q
o
is as follows: experiment of
blasting using two type of powder factor q
1
and q
2
is done two times
for each type of rock and then determining property of grain size
distribution with size x ≤ x
0
( P
1
and P
2
) corresponding to two courses
of blasting. Finally, q
0
is determined as followings:

( )
max
0
12
2
1
21
0
L
X
lgqq
P
P
lgqq
q
−
=
, kg/m
3
(3.1)
Where: P
1
, P
2
are percentages of grain size corresponding to x ≤
x
0
in two courses of blasting q
1
và q

2
, respectively.
3.2.2.2. Result of rock classification of blastability for some
limestone quarries in Vietnam
This method was applied for experiment in some limestone
quarries such as Ninh Dan – Thanh Ba – Phu Tho limestone quarry
(owned by Song Thao cement company), Van Xa – Thua Thien Hue
limestone quarry (owned by LUKS Vietnam cement company),
Thuong Tan IV – Binh Duong limeston quarry. Quarries used


10

blasthole with diameter in 76÷105 mm, bench height in 7÷15m,
bucket capacity in 2÷5 m
3
, millisecond delay non-electric blasting
method (with non-electric facility), AD-1 explosive, ratio of oversize
rock in heap less than 2÷3%.
According to experimental blasting and rock classification of
M.M.Protođiaconov, rock classification table of Prof.Dr Nhu Van
Bach & Dr. Le Van Quyen et al, rock classification of blastability can
be seen as follows:
Table 3.1: Rock classification of blastability
q
0
< 0,3 Easy
q
0
= 0,31 ÷ 0,38

Average
q
0
= 0,39 ÷ 0.46
Difficult
q
0
= 0,47 ÷ 0,55:
Very
difficult
q
0
> 0,56 Extreme difficult
3.2.3. Designing a software to rock classify of blastability


Fig 3.1- Block diagram

for determining standard
powder factor
Fig 3.2- Interface of software used
to determine rock classification of
blastability
3.3. RELATION BETWEEN POWDER FACTOR AND DEGREE OF
ROCK FRAGMENTATION
In order to evaluate efficiency of fragmentation, degree of lump
(D
tb
)is used. In case of the same blasting condition, the larger powder
factor is the smaller (D

tb
)is. Optimum requirement of grain size
within blasted rock heap depends on mining equipment fleet (bucket
capacity, method of haulage).


11

3.3.1. Proper degree of rock fragmentation
3.3.1.1. General definition of degree of rock fragmentation
According to international researches, largest size of blasted rock
is determined by loading equipment as follow:
( )
3
cp
E8,07,0D ÷=
, m (3.2)
Where :D
cp
–maximum size of blasted rock, m; E – bucket
capacity, m
3
.
Maximum size of blasted rock based on milling condition is
determined as follow:
D
cp
= (0,7 ÷ 0,8)B, m (3.3)
Where : B- minimum size of bin gate, m.
Degree of rock fragmentation is determined by diameter of grain

size within blasted heap as follow:
100
D
D
ii
tb
∑
γ
=
(3.4)
Where: D
i
– average size of grain size of “i”;
i
γ
- percentage of
grain size of “i”, %.

3.3.1.2. Determining degree of rock fragmentation
Degree of rock fragmentation can be determined by methods as
followings:
- Determining average size of blasted rock D
tb
by statistical power
method.
- Determining average fragment size of blasted rock D
tb
by semi-
experimental method of V.M. Kuzonhetxov.
- Determining average fragment size of blasted rock D

tb
according
to method of B.N. Kutuzov.
- Determining average fragment size of blasted rock D
tb
average
method from evaluating size of blasted rock in practice.
3.3.1.3. Evaluation of degree of rock fragmentation
- Degree of rock fragmentation is reasonable if it ensures that
total cost of a production unit in mining is minimum.
minKEC
n
1i
i
n
1i
i
→+
∑∑
==
; (3.5)
Where: C
i
– production unit of one m
3
of rock according to
phases including: primary blasting and drilling; loading, hauling and
overisize rock breaking đ/m
3
; K

i
– basic cost of one m
3
of rock


12

according to phases including: drilling; loading, hauling and milling,
đ/m
3
; E – coefficient of investment efficiency.
3.3.1.4. Proper degree of rock fragmentation for quarries
In order to determine a proper degree of rock fragmentation
according to technical conditions of quarries, it is possible to use
some method as followings:
- According to bucket capacity:
3
tb
E)2,015,0(d ÷=

(3.6)

Where: E – bucket capacity, m
3

- Determining average size of blasted rock according to method
of B.N. Kutuzov
3
o

qc
cp
tb
V
V
14
D
D








−
=

(3.7)
Where : V
qc
– percentage of size of blasted rock, %; V
o
–
percentage of natural cracking mass in bank being larger than
required size of blasted rock.
According to statistical and analytical result of data from quarries
in Vietnam, application of equation (3.7) is suitable to determine
degree of rock fragmentation. Here, required size of blasted rock D

cp
is determined based on milling condition. Maximum size of blasted
rock depends on type and capacity of milling machine.
CHAPTER 4: DETERMINATION OF REASONABLE POWDER
FACTOR FOR LIMESTONE QUARRIES IN VIETNAM
4.1. Research to the relationship between powder factor with element
affect.
Determination of reasonable powder factor for limestone quaries
in Vietnam to have research to relationship between powder factor
with affecting element to blasting.
4.1.1. Research to relationship between powder factor with
explosives


13

For the selection explosives based on:
- The first is characteristic of explosives
- The second is the cost of explosives
When determining powder factor by using other explosives, it is
different from standard explosives must mention the conversion
coefficient because the explosive energy is different
4.1.2. Research to relationship between powder factor with rock
properties
According to experimental and theory of blasting, the rock
properties is the most important and directly affect to calculate
powder factor.
4.1.3. Research to relationship between powder factor with
blasting parameters
4.1.3.1. Relationship between powder factor with charge diameter

Definition of charge diameter that directly affect to
Fragmentation size and cost of product. However with the required of
Fragmentation size should be increasing charge diameter because the
large diameter overcome high bench and then extending drilling
patterns, to reduce cost of drilling.
4.1.3.2. Relationship between powder factor with hole spacing
Through results research about the relationship level of powder
factor with blasting parameters as charge diameter, bench high, hole
spacing are little change, because there are depend on blasting
requirements.
4.1.4. Relationship between powder factor with blasting methods
When calculating powder factor, blasting method is not the
number variables of function powder factor, which is the only
coefficient depends on blasting conditions.
4.1.5. The relationship for the determination of Powder factor -
Fragmentation size
This is important factor for determination of reasonable powder
factor. According to experimental and theory of blasting can confirm
this relationship is linear function, it means:
q = ϕ (d
tb
) = ad
tb
+ b (4.1)



14

4.1.6. The relationship for the
determination of Powder factor
- environment
To protect the environment
when blasting in limestone
quarries as follows:
- Using suitable types of
explosives
- Using suitable powder factor

Fig 4.1- Powder factor depend
on Fragmentation size
- Using appropriate blasting parameters
- Using reasonable blasting methods
4.2. DETERMINATION OF REASONABLE POWDER FACTOR
FOR LIMESTONE QUARRIES IN VIETNAM
4.2.1. Analysis, assessment and classification of the elements
affecting to powder factor
Powder factor depends on rock properties, explosive types,
blasting methods, blasting parameters, and required fragmentation.
The influence of each factor to powder factor is different, based on
these properties it can be divided into two groups.
Group one: The factors
directly influencing to reasonable
powder factors:
- Rock properties, (rock
strength, rock fracture);
- Required fragmentation,
(average fragment size);
These factors are variables

of the function of reasonable
powder factors
Group two: The factors
indirectly influencing to reasonable

Fig 2- Outline of illustrations
function of powder factor and
affecting factors
x
1,
x
2
- The variables; k
1
, k2- the
affecting factors


15


powder factors, it means that the values of powder factor change in
certain range.
The powder factor is a function Y, the affecting factors are
variables x
1
, x
2
, May be function of powder factor such as:
Y = f(x

1
, x
2
,….) (4.2)
4.2.2. Definition of optimum explosives
Based on the requirements and characteristics of limestones
quarries in Vietnam, using standard explosives are ANFO to
calculation
4.2.3. Method of determination of powder factor for limestone quarries
4.2.3.1. Powder factor depends on blasting requirements
The research results indicated the distribution law of particle size
and the function of powder factor with average fragment size is linear
function:
q
cn
= ad
tb
+ b (4.3)
Where- q
cn
is technical powder factor, kg/m
3
; d
tb
is average
fragment size, m; a, b is empirical coefficients, it found from
empirical blasts.
For determination relationship between power factor -
Fragmentation size, author carry out blasting test at Ninh Dan
limestone quarry, Thuong Tan limestone quarry, Yen Duyen

limestone quarry as follows:
- Rock hardness equal 6 ÷ 12, degree of fracturing belong to level
II III, IV;
- After each blast carried out photographed and monitoring muck
loading. Used Autocad và Spit – Desktop software for determination
fragment size (Fig 4.3). The results of determination fragment size
shown on table 4.1 and graph of fragment size distribution shown on
fig 4.4.


16

Table 4.1: The results of
determination fragment size


Fig 4.3- interfaces software of Spit
– Desktop
- From the results of blasting test at limestones quarries, we
builded the functional relationship between the average fragment size
with powder factor is shown on fig 4.5, 4.6, 4.7.


Fig 4.4- Graph of fragment size
distribution

Fig 4.5- Powder factor -
Fragmentation size relationship at
Ninh Dan limestone quarry

Fig 4.6- Powder factor -
Fragmentation size relationship at
Thuong Tan IV limestone quarry

Fig 4.7- Powder factor -
Fragmentation size relationship at
Yen Dunyen limestone quarry


17

Base on results blasting test, if other affecting factor is not
changing as rock hardness, type of explosives, fracturing, then only
changing fragment size, to realize:
- When d
tb
≈ 0 then q
cn
= q
max
= b
- When q
cn
= 0 → 0 = ad
max
+ b
→
max
max
d

b
a
a
b
d −=→−=

Where: d
max
– Diameter of medium fracture block in the rock
mass
Equation (4.2) then is becomes:
b
d
d
bq
max
tb
cn
+−=
(4.4)
- According to the statistics from blasting at limestone
quarries, maximum of powder factor (q
max
) equal 0,8 kg/m
3
. Then
q
cn
= q
max

= 0,8kg/m
3
→ b = 0,8, The equation (4.3) becomes:

8,0
d
d
8,0q
max
tb
cn
+−=
(4.5)
4.2.3.2.
Powder factor depends on rock hardness f
The rock strength is estimated by hardness coefficient f, (M.M.
Protodiaconov's classification). When hardness coefficient
increasing, Powder factor also increasing. When mentioning the
hardness coefficient, the formula of Powder factor is determined as
follows:
q
1
= k
1
.q
cn
(4.6)
According to the statistics, blasting test determination relationship
between rock hardness power factor q
cn

and q
1
shown on table 4.2
Table 4.2: Relationship between rock hardness power factor q
cn
and q
1

Rock hardness (f) 6 7 8 9 10 11 12
Technical powder
factor q
cn
, (kg/m
3
)
0,25 0,28 0,32 0,35 0,40 0,45 0,48
Powder factor q
1
,
(kg/m
3
)
0,25

0,30
4
0,35
4
0,39
7

0,46
5
0,53
5
0,58
2
q
1
/q
cn

1 1,07 1,10 1,13 1,16 1,18 1,21


18

From data in table 2 determine the relationship between quotient
q
1
/q
cn
and rock hardness such as:
q
1
/q
cn
= 0,635.f
0,262
(4.7)

Where q
1
/q
cn
is hardness coefficient. This is coefficient k
1
need to
find.
The equation (4.6) becomes:
4
1
f635,0k ×=
(4.8)
The powder factor can be determined by the following formula

cn
4
cn11
qf635,0qkq ××=×=
(4.9)
4.2.3.3. Powder factor depends on rock
density
When mentioning the rock density, the powder factor can be
determined by the following formula.
q
2
= k
2
.q
1

(4.10)
For the limestons quarries in Vietnam, average rock density is 2,6
t/m
3
. According to the theory of blasting and blasting test coefficient
k
2
determined by the following formula:

6,2
k
đ
2
γ
=
(4.11)
Replace (4.10) in (4.9) and equation (4.9) then is becomes:

cn
4đ
2
qf635,0
6,2
q ×××
γ
=
(4.12)

4.2.3.4.
Powder factor depends on type of explosives

When mentioning the type of explosives. Using coefficient k
3
is
relative heat of explosives:
k
3
= Q
tc
/Q (4.13)
Where: Q- heat of explosives using, Kcal/kg; Q
tc
- heat of
standard explosives ANFO.
Powder factor can be determined by the following formula:
cn
4đ
33
qf635,0
6,2
kq ×××
γ
×=
(4.14)


19

4.2.3.5. Powder factor depends on blasting method
Today, the delay initiation method is used in all of the limestone

quarries in Vietnam because of its many advantages. The most
common value of k
4
when using delay initiation method will
generally lie in the range of 0.85 to 0.95. Powder factor can be
determined by the following formula:

cn
4đ
343
qf635,0
6,2
kkq ×××
γ
××=

(4.15)
4.2.3.6. Powder factor - blasting parameters and environment
relationship
The relationship between powder factor - blasting parameter and
environment is indirectly. Method of determination of reasonable
powder factor (q
hl
, kg/m
3
) does not take into account this relationship
and also not shown in this formula.
From the results of the formulas (4.4 ÷ 4.14) to establish the
final formula of determination of reasonable powder factor is
becomes:

43
đ
max
tb
4
hl
kk
6,2
)8,0
d
d
8,0(f653,0q ×
××
××
××
×
γ
γγ
γ
×
××
×+
++
+−
−−
−×
××
×=
==
=

, kg/m
3
(4.16)
The formula determination of reasonable powder factor shows
full factors of influence on powder factor and meets the requirement
and purposes of the blast as when changing fragment size, rock
property, explosives type and condition of blasting for limestone
quarries in Vietnam.
The results of calculations for a number of limestone mines are
suitable with actual results. The problems of this formula need to be
more multiple blasting experimental to determine exactly influence
coefficient.
4.3. Build program calculates powder factor, blasting parameters
and blasting patterns
From the study, author have built the software calculates powder
factor, blasting parameters and blasting patterns. Programs written by


20

VBA / Excel language help engineers easy to use for calculating
blasting parameters, blast log quickly, exactly and reliably.
4.3.1. Software structure
Software including 4 parts:
- Part 1: General Information
- Part 2: Determination of reasonable powder factor
- Part 3: Determination of blasting parameters
- Part 4: Drawing blasting patterns
4.3.2. Introduce some interfaces and results calculated by the
software

Fig 4.8- Block Diagram of software



Fig 4.9- General Information

Fig 4.10- Determination of
reasonable powder factor

Fig 4.11- Drawing blasting
patterns


21


ÐKN
400400400400400
400400400400400
17 17 17 17
42 42 42 42 42


Fig- 4.12- Delay blasting patterns
using non electric detonation
Fig- 4.13- Delay blasting
patterns using electric
blasting cap

.
Fig- 4.14. Interfaces of blast log
GENERAL CONCLUSION
1. Rock blasting is the first step in mining, especially in
limestone quarries. One of the most important blasting parameters
needs caring is powder factor. This parameter has considerable
influence on other blasting parameters and the environmental
impacts.
2. There are various natural and technological factors that
influence on the powder factor. Two groups classify the elements:
fluctuation factors and constant factors. In different condition, the


22

powder factor is calculated based on the quantitative relationship of
the mentioned factors.
3. The most factors influencing on powder factor is blasting
index and
- Blasting index is specified by the standard powder factor q
0
.
then the size of blasted rock is a linear distributed). Software by the
author can help to classify the blasted rock by blasting index in
different in limestone quarries.
- Required fragment size in the limestone quarries can be
calculated under different technical condition (by the formular of
Prof. Kutuzov, in which D
cp

is depended on the crushing and
screening conditions).
4. Conditions of the limestone quarries in Vietnam the suitable
explosives is ANFO (Explosives produced by Vietnam). The
conversion coefficient is calculated by the energy index of the
detonation to the ANFO explosive energy.
5. The technical powder factor (q
cn
), which is defined by the
required fragment size (d
tb
)

and the fracture block in the rock mass
(d
max
), is the basis to define the powder factor of any condition. There
is a linear relation between q
cn
and d
tb
(q
cn
= ad
tb
+ b).
6. The appropriate powder factor in limestone quarries is defined
by theoretical and experimental measure, based on the technical
powder factor q
cn

. Some factors, such as the strength, the fracture, the
density, fragment size, are set in the technical powder factor as
fluctuation factors; the others are mentioned constant factors.
7. From the suggested formular of the powder factor, other
blasting parameters and blasting log can be solved in the software
that the author mentioned in the dissertation.
PUBLICATIONS
1. Nguyen Dinh An (2004), Determination of reasonable powder
factor for surface mining in Vietnam, Proceedings of mining science
and technology conference 19
th
, Hanoi University of Mining and
Geology. p 37-41.


23

2. Nhu Van Bach, Nguyen Dinh An, Nhu Van Phuc (2006).
Blasting design for obtaining desired fragmentation at Apatite mine
in Lao Cai, Journal of mining and geology in science and technology,
Hanoi University of Mining and Geology. p 11-14.
3. Nguyen Dinh An, Bui Xuan Nam (2006). Computer simulations
of delay blasting, Journal of mining and geology in science and
technology, Hanoi University of Mining and Geology. p 74-75
4. Nhu Van Bach, Lê Văn Quyển, Bui Xuan Nam, Nguyen Dinh
An, Nhu Van Phuc (2006). Reduce of ground vibration in blasting at
Nui Beo surface coal mines. Journal of mining and geology in
science and technology 14th edition, Hanoi University of Mining
and Geology. p 58-62
5. Nguyen Dinh An, Tran Khac Hung (2010). Determination of

reasonable powder factor for limestone quarries in. Mining industry
journal, 5th edition. Vietnam mining science and technology
association. Ha Noi, p 36-38.
6. Nguyen Dinh An, Nhu Van Bach, Tran Quang Hieu, Nhu Van
Phuc (2010). Improve blasting efficiency and minimizing bad impacts
on environment for Van Xa limestone quarry, Proceedings of mining
science and technology conference, Hanoi University of Mining and
Geology, p. 3-9
7. Nguyen Dinh An, Tran Quang Hieu, Tran Khac Hung (2011),
Methods for determining peak particle velocity of ground vibration
caused by blasting in surface mining, Proceedings of national
conference in mining science and technology 22
th,
Vietnam mining
science and technology association, p 265 – 269.
8. Nguyễn Duy Thanh, Nguyen Dinh An, Tôn Thatt Hàm, Đinh
Ngọc Hung, (2011), Actual status of the exploitation limestones
quarries in Thua Thien Hue province, Proceedings of
national conference in mining science and technology 22
th
. Vietnam
mining science and technology association, Nha Trang – Vietnam,
p 229-232.


24

9. Nguyen Dinh An (2011), Methods of classification of
Blastability, Mining industry journal, 6th edition. Vietnam mining
science and technology association. Ha Noi. Tr. 45-47.

10. Nguyen Dinh An, Tran Khac Hung (2011). Reduce of ground
vibration in blasting at Nui Beo surface coal mine. Proceedings of
The International Symposium on Earth Science and Technology
2011, 6-7 December 2011, Kyushu University, Fukuoka, Japan
11. Nguyen Dinh An , Nhu Van Bach, Nguyen Van Sang, Tran
Khac Hung, Tran Dinh Bao (2012). Determination of reasonable
powder factor for Vietnam limestone quarries. The 2nd International
Conference on Advances in Mining and Tunneling. Hanoi, August
23-25, 2012, Publishing House for Science and Technology, p 350-
352 (ISBN 978-604-913-081-6).
12. Nhu Van Bach, Nguyen Dinh An, Le Qui Thao (2012).
Analyzing the factors affecting to the vibration when blasting with
non-electric detonators. The 2nd International Conference on
Advances in Mining and Tunneling. Hanoi, August 23-25, 2012.
Publishing House for Science and Technology. P. 338-340 (ISBN
978-604-913-081-6).
13. Nhu Van Bach, Nguyen Dinh An, Lê Qui Thao, Tran Dinh Bao
(2012), Developing technology of large hole drilling diameter for
limestone quarries in Vietnam, Proceedings of mining science and
technology conference 20
th
, Hanoi University of Mining and
Geology. P. 141.
14. Nhu Van Bach, Nguyen Dinh An, Bui Xuan Nam, Tran Khac
Hung (2012), Reduce of ground vibration in blasting is the use of
none electric blasting, Journal of mining and geology in science and
technology 38
th
edition, Hanoi University of Mining and Geology. p
25 - 28.

15. Nhu Van Bach, Nguyen Dinh An, Tran Khac Hung (2012),
Selection of initiation point and delay blasting sequence in order to
reduce of ground vibration in blasting is the use of none electric
blasting, Mining industry journal, 2th edition, Vietnam mining
science and technology association, p 19 – 23.