International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 04, April 2019, pp. 2259–2266, Article ID: IJCIET_10_04_235
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ISSN Print: 0976-6308 and ISSN Online: 0976-6316
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APPLICATION OF METHODS OF MINE
AEROGASDYNAMICS FOR SIMULATION OF
PROPAGATION OF BLAST WAVE IN JOINT
JUNCTIONS OF MINE WORKINGS
Vladimir Alekseevich Rodionov
Ph.D., Associate Professor, Department of Industrial Safety,
Saint Petersburg Mining University
Russian Federation, 199106, Saint Petersburg, Vasilievski Ostrov, 21 line, 2
Evgeniy Olegovich Sharavin
Ph.D. Student at the Department of Mine-Rescue Business and Explosion Safety, Saint
Petersburg University of State Fire Service of EMERCOM of Russia
Russian Federation, 196105, Saint Petersburg, Moskovskiy Prospect 149
Ekaterina Andreevna Kochetkova
Ph.D., Associate Professor, Department of Industrial Safety,
Saint Petersburg Mining University
Russian Federation, 199106, Saint Petersburg, Vasilievski Ostrov, 21 line, 2
ABSTRACT
This paper reviews the processes of blast wave propagation in joint junctions of
capital and preparatory mine workings, the blast wave is formed in blast of air-coal
mixture in the seams of horizontal and inclined occurrence. Methods of mine
aerogasdynamics applicable to various geometrical combinations of joints, were used
for simulation and calculations. At the initial stag of doing the research work,
simplified variants of rectangular types of joints were selected for studying
aerogasdynamic and thermophysical processes emerging in blast of aerosols of coal
dust. The source data for building a model in ANSYS FLUENT software were adopted
based on the experimental studies conducted by the authors on identifying the
damaging factors of blast in the laboratory device for conducting blasts of air-coal
mixture in confined space. The maximal pressure of the blast and the speed of
pressure build-up in blast was identified in a 20-litre spherical blast chamber. It was
identified that the maximal blast pressure emerges in the laboratory device in forced
blast in the volume of coal dust of 63-94 micrometers. As a result of constructing the
model, according to the obtained experimental data, the probability of emergence of
reflected waves is established. Emergence of reflected waves, according to the model
built by means of ANSYS FLUENT, causes formation of local zones of increased
pressure. It was established that the highest pressure develops in the front of blast
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Vladimir Alekseevich Rodionov, Evgeniy Olegovich Sharavin, Ekaterina Andreevna Kochetkova
waves in their mutual encounter incident wave+ reflected wave and reflected
+reflected blast waves. In this respect, the biggest hazard in blast pressure build-up in
the blast wave front is formed in mine workings of rectangular T-shaped intersection.
As a result of calculation and modelling, the fact of the consistency of the obtained
experimental results with the actual process of blast wave propagation in elastic
media, was identified. In addition, the obtained experimental results in computer
simulation, with use of ANSYS FLUENT software, mine aerogasdynamic processes of
blast wave propagation, enable to calculate promptly and efficiently fairly complex
joint junctures of mine workings. Work in this area will be continued.
Key words: mine aerogasdynamics, mine workings, blast wave, ANSYS FLUENT,
explosive coal dust, maximal blast pressure, air-coal mixtures.
Cite this Article: Vladimir Alekseevich Rodionov, Evgeniy Olegovich Sharavin,
Ekaterina Andreevna Kochetkova, Application of Methods of Mine Aerogasdynamics
for Simulation of Propagation of Blast Wave in Joint Junctions of Mine Workings,
International Journal of Civil Engineering and Technology 10(4), 2019, pp. 2259–
2266.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=4
1. INTRODUCTION
This work is of relevance due to the complexity of forecasting the implications of one of the
most hazardous manifestations of undreground blast – blast wave.
The magnitude of destruction depends on many factors which are difficult to identify
theoretically, including change in the intestity and direction of blast wave propagation [1-3].
Complexity of simulation of such dynamic processes is related to network of mine
workings constant variation and
increasing sophistication, which requires constant
monitoring and creation of new mathematical models [2, 4-10].
Emergence of up-to-date means of computer simulation enables to study multiple hub
connections and take into account many factors which accompany blast war manifestation [9,
11-13]. In so doing, high degree of vizualization of various forms of the dynamic process of
pressure manifestation is achieved, which enables to estimate the blast parameters
qualitatively and quantitatively. [3, 5, 13-15].
Purpose of work
Creation of physical and mathematical two-dimensional model in ANSYS FLUENT software
for simulation of the pattern of blast wave formed in air-coal mixture blast, in various junction
junctures of mine workings.
2. METHODOLOGICAL FRAMEWORK
In order to describe the blast wave propagation in this model, we will use the elementary
theory of shock tube [3, 9, 14-17]. According to this theory, we use two constants for
mathematical simulation: molecular weight - and adiabatic index - .
Constants
and
are related to the low-pressure area, and constants
and
are
related to the high-pressure area, respectively,
and
are initial pressures, and
(Fig.1).
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Application of Methods of Mine Aerogasdynamics for Simulation of Propagation of Blast Wave
in Joint Junctions of Mine Workings
Figure 1. General scheme of setting the conditions of blast wave propagation in ANSYS FLUENT
software: 1 – Boundary condition of pressure inlet; 2- high pressure area; 3- border between areas; 4 –
boundary conditions of walls; 5 – low pressure area.
In addition, for calculation simplification, we consider the shock tube as heat-insulated,
and movement of gas as adiabatic.
According to this theory, we have the following equation, which we
will subsequently use for simulation:
(
)[
(
)
(1)
]
⁄ is the set initial ratio of the pressures in different areas of the pipe;
are the indicators of adiabat for the area of low and high pressure;
is the
molecular weight for the area of low and high pressure;
is Mach number of blast wave:
where
(2)
where
is the flow rate;
is the local sound velocity.
√
(3)
The key stages of mathematical simulation in ANSYS FLUENT for setting the blast
wave:
1. Creation of required geometrical model;
2. Breaking the model down into elements (generation of calculation grid);
3. Setting the boundary conditions, material and pressure;
4. Selecting a necessary equation for solving and optimizing the parameters corresponding to
the equation;
5. Defining the blast wave parameters for building a reliable model of blast wave propagation
with using reference data;
6. Output and visualization of calculation data.
To study the issues of the possibility to the mathematical tools implemented by means of
applied software ANSYS FLUENT designated for studying the mine aerogasdynamics,
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Vladimir Alekseevich Rodionov, Evgeniy Olegovich Sharavin, Ekaterina Andreevna Kochetkova
namely, the processes of blast wave propagation in joint junctions of mine workings, we have
made several assumptions. Taking into account the fact that we are at the beginning stage, we
have selected rectangular joints from all possible multitude of joints.
In our view, this approach will enable us to model the processes of the emergence and
propagation of the blast wave along the mine workings’ space. In addition, it will enable us to
identify in more detail and with higher reliability the areas of blast build-up and fading,
manifestation of reflected blast war, and also to identify the counter areas of blast wave fronts,
which have higher blast pressure than the initial maximal blast pressure [15-20].
One of the conditions for the model validity and evaluating the possibility of applying the
results in practice, is the need of identifying the characteristics of detonation combustion of
coal dust taken from the active workings of coal mines [7-10, 15, 18-21]. For this reason, in
order to enhance the practical component, we did research on identifying the damaging blast
factors of air-coal mixtures of mines. Using the obtained experimental data, we determined
the transformation coefficient. By means of this coefficient, it is possible to compare the
calculation parameters of the process of blast wave propagation with the data obtained by
using during constructing the model [18, 22-24].
In performing our research, we relied on the recommendations and data of other authors
studying similar issues, these recommendations are described in several studies [2, 3, 14, 17].
Scientifically proven selection of stone dust fraction was performed in line with the data of
studies [5, 13, 18], and is confirmed by the results we obtained.
3. RESULTS AND DISCUSSION
According to studies [5, 13, 18], for solving the problem of determining he maximum blast
pressure, the velocity of blast pressure build-up and the transformation coefficient, and also of
the source data adjustment, we conducted tests in the laboratory unit which is a 20-litre
combustion chamber for studying the blast parameters of dust and gas mixtures of various
concentrations. The physical appearance of the main unit of the device which belongs to St.
Petersburg Mining University, are presented in Figure 2.
Figure 2. Physical appearance of 20-litre combustion chamber:
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Application of Methods of Mine Aerogasdynamics for Simulation of Propagation of Blast Wave
in Joint Junctions of Mine Workings
1 - base (stand); 2 – multiphase valve of dust/air inlet;
3 – outlet of recirculation water; 4 – vacuum gauge; 5 – safety valve; 6 – handle of safety lock
of safety valve;
7 – twist handles of chamber lid; 8 – inlet for recirculation water;
9 – inspection hole; 10 – pressor sensor input; 11 – vessel for dust samples (pre-compression
vessel); 12 – ignition wire contacts in the removed position.
The authors of the studies [3, 5, 18] determined that fractions of 0-45 micrometers have
the highest blast pressure, but the formation of such fractions in the longwall space is not
plausible. This is explained by the fact that the smaller fractions are removed by air
aerodynamic flow, both by the application of irrigation systems to the face area by the surface
miner working elements, and by application of the dust suppression system. Obtaining the
fractions by the forced method when conducting dry granulometric sieving is complicated
because of particle adhesion and clogging sieve cells. For this reason, in the source data,
during the construction of the models, the dispersion of dust of 63-94 micrometer fraction was
taken into account, with which, the maximal damaging blast factors develop, which is
confirmed by the authors of the following studies [3, 5, 13, 18, 23, 24].
Conditions for conducting the experiment

Size distribution of coal dust sample: 63-94 μm;

Dispersion overpressure Pd = 2 MPa;

Initial pressure Pi = 0.1013 MPa (preevacuation of the explosion vessel down to 0.04 MPa);

Initial temperature Ti = 20°C0 (water cooling);

Ignition delay time tv = 60 ms;

Ignition source: chemical igniter of energy 10 kJ.
As a results of the performed research work, it was established that during blast of mine
coal dust fraction of 63-94 micrometers in dispersity: 1. The highest blast pressure is achieved
at the concentration of 250 g/m3; 2. The maximal blast pressure is Рm=0.76 MPа; 3. The
pressure build-up velocity during the explosion dP/dt=48.97 MPа/s.; 4. Transformation
coefficient Km=13.29 МPа*m/s.
Taking into account the abovementioned conditions and the obtained experimental data in
ANSYS FLUENT software for mine workings of rectangular and rectangular branch, a model
was constructed, its results are represented below in a graphical form.
Figure 3. Results of visualization of calculating pressure gradient of workings’ rectangular
intersection
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Vladimir Alekseevich Rodionov, Evgeniy Olegovich Sharavin, Ekaterina Andreevna Kochetkova
Figure 4. Results of visualization of calculating pressure gradient of workings’ branch
As a result of constructing the models for rectangular intersection and rectangular branch
of mine workings, we identified the emergence of reflected waves. In case of rectangular
intersection, the pressure value at the encounter of incident blast wave and reflected blast
wave, are within the acceptable limits (blue area, see Figure 3). In a rectangular branch, we
observe pressure build-up in the front of blast wave formed by the incident and reflected blast
waves (see Figure 4), and the excessive pressure value is several times higher (up to 0.9
MPа) than in the front of the incident blast wave.
6. CONCLUSIONS
The results obtained by us, suggest that in mine workings intersecting each other at an acute
angle, the emerged blast wave, under certain circumstances, will be extinguished by explosion
protection devices more effectively.
The results of simulation are in line with the pattern of the blast wave of the real
experiments presented in Album of Fluid Motion [9], hence, the used mathematical model,
with a slight adjustment, can also be used for two-dimensional simulation of the blast wave
pattern for other cross-sections of mine workings (trapezoidal, arched, round and others).
Thus, computer simulation with the use of ANSYS FLUENT for mathematical simulation
of blast waves, enables to calculate promptly and effectively fairly complex joint junctures of
mine workings.
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