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 C
Trang 1UNIVERSiTY 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
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
Trang 2INTRODUCTION
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 m3 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 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
Trang 3Research 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 (qcn) determined according to
required degree of rock fragmentation (dtb) and degree of crack (dmax)
is a foundation to determine powder factor for any blasting
conditions Relation between qcn và dtb is linear
3 Reasonable powder factor in quarry mining is determined by
technical powder factor (qcn) 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
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
Trang 41.3.3 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
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 No6 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
Trang 5using 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
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
Trang 6CHAPTER 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 qo Based on this factor, grain size of
blasted rock heap distributes as a line on graph
Method of determination of qo is as follows: experiment of
blasting using two type of powder factor q1 and q2 is done two times
for each type of rock and then determining property of grain size
distribution with size x ≤ x0 ( P1 and P2) corresponding to two courses
of blasting Finally, q0 is determined as followings:
max
0 1 2
2
1 2 1 0
L
X lg q q
P
P lg q q q
−
Where: P1, P2 are percentages of grain size corresponding to x ≤
x0 in two courses of blasting q1 và q2, 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
blasthole with diameter in 76÷105 mm, bench height in 7÷15m, bucket capacity in 2÷5 m3, 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
q0 < 0,3 Easy q0 = 0,31 ÷ 0,38 Average
q0 = 0,39 ÷ 0.46 Difficult q0 = 0,47 ÷ 0,55: difficult Very
q0> 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 (Dtb)is used In case of the same blasting condition, the larger powder factor is the smaller (Dtb)is Optimum requirement of grain size within blasted rock heap depends on mining equipment fleet (bucket capacity, method of haulage)
Trang 73.3.1 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:
cp 0 , 7 0 , 8 E
Where :Dcp–maximum size of blasted rock, m; E – bucket
capacity, m3
Maximum size of blasted rock based on milling condition is
determined as follow:
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
Dtb ∑γi i
Where: Di – average size of grain size of “i”; γi- 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 Dtb by statistical power
method
- Determining average fragment size of blasted rock Dtb by
semi-experimental method of V.M Kuzonhetxov
- Determining average fragment size of blasted rock Dtb according
to method of B.N Kutuzov
- Determining average fragment size of blasted rock Dtb 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
min K
E C
n
1 i i n
1
i
∑
=
=
Where: Ci – production unit of one m3 of rock according to
phases including: primary blasting and drilling; loading, hauling and
overisize rock breaking đ/m3; Ki– basic cost of one m3 of rock
according to phases including: drilling; loading, hauling and milling, đ/m3
; 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 (0,15 0,2) E
Where: E – bucket capacity, m3
- Determining average size of blasted rock according to method
of B.N Kutuzov
3
o qc
cp tb
V
V 1 4
D D
−
=
(3.7)
Where : Vqc– percentage of size of blasted rock, %; Vo– 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 Dcp
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
Trang 8For 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:
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
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
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
Trang 9powder 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 x1, x2, May be function of powder factor such as:
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:
Where- qcn is technical powder factor, kg/m3; dtb 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
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
Trang 10Base 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 dtb ≈ 0 then qcn = qmax = b
- When qcn = 0 → 0 = admax + b
→
max max
d
b a a
b
Where: dmax – Diameter of medium fracture block in the rock
mass
Equation (4.2) then is becomes:
b d
d b q
max
tb
- According to the statistics from blasting at limestone
quarries, maximum of powder factor (qmax) equal 0,8 kg/m3 Then
qcn = qmax = 0,8kg/m3 → b = 0,8, The equation (4.3) becomes:
8 , 0 d
d 8 , 0 q
max
tb
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:
According to the statistics, blasting test determination relationship
between rock hardness power factor qcn and q1 shown on table 4.2
Table 4.2: Relationship between rock hardness power factor q cn and q 1
Technical powder
factor qcn, (kg/m3) 0,25 0,28 0,32 0,35 0,40 0,45 0,48
Powder factor q1,
(kg/m3) 0,25
0,30
4
0,35
4
0,39
7
0,46
5
0,53
5
0,58
2
q1/qcn 1 1,07 1,10 1,13 1,16 1,18 1,21
From data in table 2 determine the relationship between quotient
q1/qcn and rock hardness such as:
Where q1/qcn is hardness coefficient This is coefficient k1 need to find
The equation (4.6) becomes:
4
1 0,635 f
The powder factor can be determined by the following formula
cn 4 cn
1
1 k q 0,635 f q
When mentioning the rock density, the powder factor can be determined by the following formula
For the limestons quarries in Vietnam, average rock density is 2,6 t/m3 According to the theory of blasting and blasting test coefficient
k2 determined by the following formula:
6 , 2
γ
Replace (4.10) in (4.9) and equation (4.9) then is becomes:
cn 4 đ
6 , 2
4.2.3.4 Powder factor depends on type of explosives
When mentioning the type of explosives Using coefficient k3 is relative heat of explosives:
Where: Q- heat of explosives using, Kcal/kg; Qtc- heat of standard explosives ANFO
Powder factor can be determined by the following formula:
cn 4 đ
3
6 , 2 k