Ijciet 10 02_029

http://www.iaeme.com/IJCIET/index.asp 261 editor@iaeme.com
International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 02, February 2019, pp. 261-268, Article ID: IJCIET_10_02_029
Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=02
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
IMPACT OF THE MATERIAL TO RETAIN THE
EXPLOSION PRODUCTS ON THE QUALITY OF
THE BUILDING MATERIAL IN QUARRYING
Yurovskikh Andrey Viktorovich
Candidate of Technical Science, Manager for Internal Audit Management “Severstal
Management” Joint Stock Company, St. Klara Cetkin,
Moscow, Russia, 127299, the Russian Federation
ABSTRACT.
The paper reveals the issue of improving the quality of rock mass crushing in
quarries of building materials. The analysis of methods for improving the quality of
crushing has been performed. A method to increase the time of impact of explosion
products on a mountain massif by changing charge design has been proposed. The
method was tested and the results of explosions at the quarry of Leningrad region were
presented. The experimental data show: theoretical calculations are consistent with
experimental data and have a slight deviation; the parameters of the rock mass
disruption allow using wheel loaders in the quarry. Yet, the use of new charge designs
enabled improving the quality of crushing, namely, increasing percentage of output of
an average piece of conditioned fraction, therefore, optimizing operation of the mining
entity as a whole.
Keywords: explosion, bore-hole stemming, grade analysis and rock mass disruption.
Cite this Article: Yurovskikh Andrey Viktorovich, Impact of the Material to Retain
the Explosion Products on the Quality of the Building Material in Quarrying
International Journal of Civil Engineering and Technology, 10(02), 2019, pp. 261–268
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=02
1. INTRODUCTION
At present, due to the efforts of specialists in the field of rock mass destruction by an explosion,
in particular with the inferior blasting by the method of borehole charges, generally accepted
ideas on the mechanism of rock mass destruction by explosion, and on factors affecting the
result of destruction have been established. This resulted in creation of computational methods
and techniques that, based on the existing rock classifications with regard to various physical
mechanical and physical technical specifications, as well as properties and energy
characteristics of industrial explosives, parameters of the destroyed rock mass, allow
calculating parameters of drilling and blasting operations in one way or another, ensuring

specified quality of rock mass crushing. Development and complication of such kind of
modelling became possible only in last decades due to intensive implementation of information
technologies in mining production planning [1, 2, 19, 20].
The solution to the issue of reducing dust fraction at a mining entity to reduce mining losses
is reflected in [3, 4, 5, 23]. Modern technologies to reduce the output of dust fractions have
been used in many industries [6, 7, 8, 21, 22].
Energy costs for the listed types of blasting operations are a function of the properties of
the medium, conditions of blasting and properties of the explosive. Moreover, changing any of
the arguments of this function leads to a redistribution of the explosion energy from one type
of work to another.
Physical ideas about the mechanism of rock destruction by explosion energy, stated in these
hypotheses, and theoretical developments obtained on their basis were the basis for creating
engineering practice methods of controlling the explosion effect on the rock mass in terms of
mining practice.
Three main areas are distinguished among various methods of blasting that are used in
modern technology of blasting operations to control the degree of rock mass crushing of rocks.
The first area is related with development of rational charge structures designed to perform
a certain work (crushing, throwing, etc.) efficiently and is based on changing the mechanism
of explosion energy transfer to the surrounding solid medium.
The second area is based on the principle of energy correspondence between the energy
used for explosive destruction of rocks with different physical mechanical properties, and
energy concentrated in a unit of explosive charge [9].
The third area comprises a wide range of activities related to the integral effects of rock
mass crushing, and is based on various technological methods of blasting a set of uniform
explosive charges. This area includes operations on short-delay blasting, blasting in a clamped
medium, blasting high ledges, blasting with downhole slowing down, etc.
Today, the practice of developing quarries of building materials shows that performance of
technological processes depends on the correct solution of the issues of explosion preparation
of the rock mass (grain size distribution).
The following requirements shall be met while performing any mass explosions [10]:
- high-quality crushing of the rock mass (given the grain analysis of the blasted rock mass);
- study of the ledge bottom;
- minimum violation of the integrity of the contour part of the rock mass;
- formation of a compact pile of broken rock mass;
- protecting nearby objects against seismic impact of an explosion [11], impact of a impact-
air wave (IAW) and dispersion of rock mass pieces.
The results of experimental studies, which formed the basis for ranking parameters have
been analyzed to identify the most important parameters, change thereof produces the most
significant effect in performance of drilling and blasting operations (DBO) in the quarries of
non-metallic materials [12].
Any rock mass has its jointing:
- induced, which originates from human economic activity;
- natural, cracks thereof are formed as a result of tectonic processes (tectonic unloading
cracks), gravitational pressure of overlying rocks, in particular, cracks caused by cleavage,
weathering cracks, and leaching.

Impact of the Material to Retain the Explosion Products on the Quality of the Building Material in
Quarrying
As a result, any rock can be considered as an inhomogeneous and anisotropic medium with
a specific structure. This fact can be explained by the influence of crack systems on the physical
mechanical properties.
High density of dislocation and mechanical effects on the crystal ultimately lead to
occurrence flat discontinuities - cracks, as a result thereof crystal energy decreases, i.e. cracks
play the role of original “unloading” elements (unloading cracks) [13, 14].
Physical ideas on the mechanism of rock destruction by the explosion energy, stated in
these hypotheses, and theoretical developments obtained on their basis were the basis for
creation of engineering methods to control the explosion effect on the rock mass in terms of
mining practice [15].
Studies of the impact of the direction of detonation of explosive charges on the parameters
of stress waves led to the following conclusions:
- maximum resulting voltage at the free surface is observed at reverse initiation, and
minimum one - at direct initiation;
- when neighboring charges are initiated, we have maximum duration of the pulse itself and
its effective part;
- in rocks at hardness of f = 4÷6, it is advisable to apply a diagram with counter-initiation
of charges.
The results of [16] have showed that with the reverse initiation, stress field is distributed
more evenly over the entire height of the ledge, which ensures simultaneous arrival of the wave
to both exposed surfaces of the ledge and, as a result, leads to more intensive crushing of rocks
compared to the upper initiation.
It is known [17, 18] that stemming has a significant effect on the increase of effectiveness
of an explosion when rocks are destroyed.
Its quality, as well as practical purpose depend on the material used to make a tamping.
Ease of handling and low cost are the main requirements for the tamping material.
1.1. The suggested method to solve the issue
The main goal achieved with the use of stemming, is to increase the time of action of expanding
gaseous products of the explosion on the destroyed array and maximum use of their energy.
Traditional borehole stemming from fine rock and sand does not provide a significant
increase in locking time, as it is ejected from the borehole under the action of PD.
The active stemming, with the use thereof pressing-in of the wellhead is ensured by the
action of additional explosive charges, requires an increase in consumption of explosives and
a special technology of blasting operations.
The composition of the material stemming comprises:
- high-pressure polyethylene (HPPE) as a plasticizer;
- filler - a component of increased density (for example, SiO2);
The total length of stemming is lз=5Rз, where Rз is the radius of stemming commensurate
with the charge density. The length of spherical and conical parts are made in ratio of 1:1.
The stemming principle is as follows. After refraction of the detonation wave in the well
space, the shock wave interacts with the input diffuser. The shock wave action of PD in the
inlet diffuser leads to an increase in pressure and improvement in the stem expansion in the
borehole without significant disturbance of the shape.

After the reflection of the shock wave from the profile calculated by the equations of gas
dynamics, quasi-stationary stage of interaction between PD and tamping, characterized by the
establishment of critical parameters (subsonic speed) of their outflow through the output
conical part, occurs.
At the same time, the following is achieved:
• ensuring the time of operation of the stemming required for the maximum use of the
energy of gaseous products of the explosion
• simplifying placement of a stemming inside the well in terms of different drilling factors
and roughness of the well walls by increasing elasticity of the structure;
• a significant reduction in the cost of the product due to material savings.
The mechanism of tamping is the same as that of locking gas-dynamic device (LGDD).
The outflow of the inhibited high-temperature flow of detonation products through the exit part
after destruction of the profile walls is regulated by the resistance of the inert material due to
the forces of internal friction.
The efficiency of using such a stemming can be improved by using this design in
combination with traditional stemming from small rock of small power (length of the post)
located on the designed stemming. The downhole stemming has the shape of a cylinder, the
outer diameter thereof is commensurate with the diameter of the well, and axial internal cavity
in the form of an elongated hemisphere and a truncated cone.
Thus, the use of locking devices ensures reliable locking of the charging cavity for the time
required to maximize the use of the energy of gaseous products of the explosion and possibility
of reducing specific consumption or volume of drilling.
The diameter of the inlet is equal to the diameter of the explosive charge cavity. The profile
of the supersonic diffuser is determined by the following parameters at the input:
( )12
2
+
=
k
D
P BB
H
ρ
, (1)
PH - pressure of detonation products, BBρ - density of the explosive, D- detonation rate, k
- isentropic line curve (at the initial stage of explosion k=3).
( ) ( )101
2
1
1 λλ gRRg
F
F
B ⋅=⇒= (2)
Relative rate M=c/a (Mach number) is introduced to calculate the convergent section of
diffuser;
с – flow rate (UH) and а – local sound rate.
Inspection with regard to dimensionless velocities on the output is made with the help of
ratio:
2
2
2
1
1
1
1
1
λ
λ
⋅
+
−
−
⋅
+
=
k
kk
M . (3)
Substitution of the broken curve with a plane one forms inner profile of the diffuser from
input to critical, with subsonic velocity behind it (Fig. 1).

Quarrying
Figures 1 Calculation of geometric dimensions of stemming
l1, l2, l3 – length of separate elements of braking surface; δ1, δ2, δ3 – flow angle on these
elements; F1, FKP – cross-section area on the input and output of the item.
2. THE RESULTS
Measurements were performed in the quarries of building stone of Leningrad region of the
building stone deposit. A ledge on the second horizon was chosen as an object for the
experiment. The rechargeable units were directly adjacent, so physical and geological
parameters were the same. Then one unit was charged according to the standard diagram used
at the given entity, and the second one with the use of LGDD.
The height and width of the rock mass was assessed after the explosion.
An analysis of the grain size distribution was performed along with geometric
measurements of the collapse of the rock mass.
An optimal number of intervals needs to be determined. This value can be determined on
the basis of the available set of sieves, for a piece measurement - from the continuation of a
geometric progression with multiplier - 21/2
, and the following should be considered:
1. If there are too few intervals, the results of the study of histograms will not be able
to show the true value of the particle size distribution, since due to the large step of
the sizes of fractions many characteristic features of the distribution will be lost;
2. On the contrary, bursts and dips on the distribution function will take place when
selecting too many intervals, due to random errors.
The degree of data filtering depends on the selection of the number of intervals (for
example, 0-20 mm). This number is considered to be the most optimal, if smoothing is
combined with smoothing of the desired distribution curve.
When determining the output of the oversized fractions, the total volume of the sample V
is taken as the volume of the exploded section of the array in a dense body, determined by
surveying, and the volume of the jth sample is the difference between the volume of the
explosive block and the total volume of the oversized pieces discarded by the excavator during
FF
δ
δδ
l l l

the development of this section . The percentage yield of oversized fractions is determined by
direct counting.
A photoplanimetric method was used as the most rapid to obtain information on the grain
size distribution of the destroyed rock mass.
A linear counting method was applied during planograms processing. Parallel lines
(indicatrices) were applied to the photoplanogram horizontally and vertically, according to the
divisions of the scale tape located at the time of shooting on the collapse of the rock. The
lengths of segments per individual piece, as well as lengths occupied with fine material and
taken into account in total, were measured with regard to indicatrices. According to the
obtained lengths of segments, material was divided into fractions of fractions. The total length
of the segments for each fraction was calculated.
One can assume that the increase in the duration of the duration of the locking of detonation
products in the explosive cavity due to LGDD allows increasing the proportion of explosive
energy sued for rock crushing.
3. SUMMARY
The tasks of previous studies in this area did not include such an important issue as assessment
of the impact of the charge structure on gas-dynamic state of the explosion products in the
charging chamber, which ultimately determines the parameters of dynamic loading of the array
and its destruction.
The following research is required in this area:
1. The impact of charge design and other parameters of DBO on the rock mass crushing
and collapse formation;
2. DBO parameters that ensure economic efficiency in the course of mass explosions in
quarries of building materials. A well gasdynamic stemming delays the explosion products in
the charging chamber up to 20 msec, while delay time is determined by the diameter of the
axial channel of the stemming or its distance from the charge. It was established that when the
diameter of the axial channel is larger than the radius of the well, locking of explosion products
is not ensured. The downhole gas-dynamic stemming stops explosion products in the charging
chamber up to 20 msec, and delay time is determined by the diameter of the axial channel of
the stemming or distance of its placement from the charge. It was established that when the
diameter of the axial channel of the stemming is greater than the radius of the well, the locking
of the explosion products is not ensured.
The effect of a charge design with gas-dynamic stemming on the parameters of the collapse
of a blown-up rock mass has been investigated experimentally. For recommended designs of
charges with a diameter of 165 mm compared with the standard, the length of the disruption
increases by 8–10 m, and disruption height decreases by 2.5 m.
The disruption parameters can be adjusted by selecting the size of the air gap between the
charge and the locking gas-dynamic device.
Theoretical and practical data show that the height of the collapse decreased by 8 %, and
the width increased by 27.5 %.
The results of industrial tests of the developed structures of charges with gas-dynamic
stemming showed an increase in the fraction of useful explosion energy spent on rock
destruction, which allowed reducing the output of the oversized fraction by about 2 times and
improving quality of crushing by 15-20 % (the average size of a piece of exploded rock mass
decreased from 250 to 220 mm).

Quarrying
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Ijciet 10 02_029

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