Modelling of Aerodynamic Process for Coal Waste Dump Located in Geodynamically Dangerous Zone

Previously made evaluations show confinement of fire coal waste dumps to geodynamically dangerous zones which in this work are considered as borders of active blocks of the earth crust. According to the hypothesis under development, when disposing the dumps in geodynamically dangerous zones (GDZ), which have a high penetrating, aerodynamic relation of the dumps with the environment occurs, making the dumps firing possible. Firing of the dumps inflicts environmental, social and material damage. This research is aimed to study possible mechanism of gas mass transfer through GDZ into the body of dump on the base of computer modeling of aerodynamic processes. A relevant geometry model is developed, borderline conditions are proven and modeling of aerodynamic process is shown in the work. Taking into account actual data on location and characteristics of firing dumps of a region of Eastern Donbas (Rostov region, Russia) calculation are performed by means of ANSYS software. A dump located in GDZ is modeled. The GDZ is set in the model as a highly penetrating linear zone in the rock, which has a deep emplacement. The GDZ crosses mine fields and has an expression in relief of the Earth surface. Temperature of the rock within the dump may reach 420 degrees Centigrade. Petrophysical characteristics are taken into account in the model (porousness and permeability) of its main structural elements, dimensions of the dump, width of GDZ, difference of relief heights, depth of mine workings location under the dump. The results of the modeling show influence of the dump temperature, petrophysical characteristics of the model structural elements, depth of the mine openings location on aerodynamic processes within the dump mass. Operability of the model at the preset border conditions allows to deeply argue the hypothesis of the air intake into the dump body with consideration of the local geodynamics. According to the results obtained, geodynamic conditions of mining area where coal waste dumps are disposed, may be and are an important factor, which has an effect on creation conditions for spontaneous combustion of dumps and its further impact on environment

Critically Stressed Areas of Earth’s Crust as Medium for Man-caused Hazards

Despite advances in rockburst studies, suddenness of major geodynamic events is reported in a number of cases. Phenomenological tectonophysical model is suggested to explain some geodynamics phenomena. Prof. Petukhov I.M. suggested a concept: the Earth crust's critical stress condition is developed due to horizontal compressive forces and entrains rock strata from the sub-surface to a certain depth. The conditions that induced earthquake in 2013 at Bachat coal field in south west Kuzbass are considered in terms of critical stress developed in the top layer of the Earth crust. Estimates show that the size of the critical stress zone, produced presumably by interaction of huge (over 100 km) crustal blocks is at least 10km. Whereas critical stress zone is located in the top part of Earth's crust, mining operations in the pit including blast operations was making a direct impact on this area. Shallow occurrence of critical stress area and its size can provide insight into why mining works brought about induced earthquake with hypocenter at the depth of several kilometers. The conclusion has been made that regional areas of critical stress within rock massif developed as a result of crustal blocks interaction create hazard medium for mining

The Impact of Surface Water Seepage on Seismicity and Rockbursting in Mines

Retrospective analysis of data obtained from long-term monitoring of technogenic seismicity and rockbursts at the Apatitovy Tsirk and the Rasvumchorr Plateau deposits (Russia) showed that there is a significant (by 50% or more) increase in the number of geodynamic events during spring snowmelt periods. An upswing of seismic activity within this rock massif occurs when following conditions are true: water reserve in the snow cover on the deposit area is more than 3 × 108 m3; snowmelt period exceeds 40 days; increase in water ingress rates continues for over 5 days and total water inflow volume exceeds the previous daily measurements by at least a factor of 2. Seismic activity of the massif starts to intensify after the snowmelt develops momentum. Major induced earthquakes occurred in the years when these conditions were met (for example, in 2005 there was a magnitude 2.3 earthquake; in 2009, M = 1.6 earthquake), and more than 1000 seismic events were recorded during the snowmelt period. It has been established that when mining reaches the depths of more than 500 m, seismic events during infiltration of atmospheric precipitation begin to occur from a depth of 100–200 m and are recorded to depths of about 900 m. A possible controlling factor of the seismic activation is the reactivation of tectonic faults, which occurs under conditions of the critically stressed state of the massif, due to a decrease in their normal compression during infiltration. Retrospective analysis of the factors contributing to a strong rockburst (K = 10–11) in 1990 at a bauxite mine in the South Urals shows that prior to this disaster there was an inrush of the Ai River waters into the mine workings through a large tectonic disturbance, which has not been previously taken into account when analyzing the mechanism of this geodynamic event. The intrusion of water into the fault located in the field of regional stresses and subsequent partial relief of its fault plane from normal stresses could have triggered the rockburst with fault-slip mechanism. The study of the relationship between amount of precipitation and the degree of water encroachment into the field, on the one hand, and seismicity, on the other hand, is needed to draw up recommendations on improving geodynamic and environmental safety of mining regions in order to ensure their sustainable development

The Impact of Surface Water Seepage on Seismicity and Rockbursting in Mines

Retrospective analysis of data obtained from long-term monitoring of technogenic seismicity and rockbursts at the Apatitovy Tsirk and the Rasvumchorr Plateau deposits (Russia) showed that there is a significant (by 50% or more) increase in the number of geodynamic events during spring snowmelt periods. An upswing of seismic activity within this rock massif occurs when following conditions are true: water reserve in the snow cover on the deposit area is more than 3 × 108 m3; snowmelt period exceeds 40 days; increase in water ingress rates continues for over 5 days and total water inflow volume exceeds the previous daily measurements by at least a factor of 2. Seismic activity of the massif starts to intensify after the snowmelt develops momentum. Major induced earthquakes occurred in the years when these conditions were met (for example, in 2005 there was a magnitude 2.3 earthquake; in 2009, M = 1.6 earthquake), and more than 1000 seismic events were recorded during the snowmelt period. It has been established that when mining reaches the depths of more than 500 m, seismic events during infiltration of atmospheric precipitation begin to occur from a depth of 100–200 m and are recorded to depths of about 900 m. A possible controlling factor of the seismic activation is the reactivation of tectonic faults, which occurs under conditions of the critically stressed state of the massif, due to a decrease in their normal compression during infiltration. Retrospective analysis of the factors contributing to a strong rockburst (K = 10–11) in 1990 at a bauxite mine in the South Urals shows that prior to this disaster there was an inrush of the Ai River waters into the mine workings through a large tectonic disturbance, which has not been previously taken into account when analyzing the mechanism of this geodynamic event. The intrusion of water into the fault located in the field of regional stresses and subsequent partial relief of its fault plane from normal stresses could have triggered the rockburst with fault-slip mechanism. The study of the relationship between amount of precipitation and the degree of water encroachment into the field, on the one hand, and seismicity, on the other hand, is needed to draw up recommendations on improving geodynamic and environmental safety of mining regions in order to ensure their sustainable development

Methodology for the Selection of In-Seam Gas Drainage System for Intensive and Safe Coal Mining Synops

The article reviews general principles of selecting efficient solutions of in-seam gas drainage and provides analytical foundation for selecting parameters of in-seam gas drainage with due account for estimated output of production face. The schemes of degassing preparation at the production facilities of Kuzbass are presented. Recommendations are provided on the selection of in-seam gas drainage methods at the production areas of Kirova Mine, JSC SUEK-Kuzbass

Improvement of Intensive In-Seam Gas Drainage Technology at Kirova Mine in Kuznetsk Coal Basin

One of the ways to resolve the “green energy-economic development” dilemma, in which the coal industry is situated, is by the improvement of technologies and the integrated use of extracted resources, including methane gas as a clean energy source. Using the example of the Kirova mine, located in Kuznetsk coal basin—one of the ecologically unfavorable coal mining regions of Russia—this article discusses an integrated technology for the extraction of coalbed methane (ECBM), which makes it possible to reduce greenhouse gas (methane) emissions and improve the safety and intensity of coal mining. The Kirova mine, with its 3 Mt production in 2019, is one of the coal mining leaders in Russia. The available mining equipment has the potential to significantly increase the output; however, gas is a limiting factor to this. The customary approaches to coal seam degassing have already been petered out. The miners and mine science are facing a challenge to validate and test an alternative technology to ensure effective in-seam gas drainage prior to vigorous mining. This article gives an account of the improvement track record of the in-seam gas drainage technology used to pre-treat coal seams for intensive and safe extraction. This technology suggests, at the first stage, hydraulic loosening of the target coal seam through wells drilled from the surface (SSHL), then hydraulic fracturing (HF) of the coal seam through the boreholes drilled from underground development headings, followed by methane extraction from the high-permeability coal-gas reservoir created through standard in-seam gas drainage underground wells. Results are presented in this paper of field testing of the improved SSHL technique. Findings are presented on the effective parameters of the HF technology. Methodological recommendations are offered for selecting viable in-seam gas drainage technology

Investigation of the influence of the geodynamic position of coal-bearing dumps on their endogenous fire hazard

The paper investigates the hypothesis according to which one of the factors influencing the spontaneous combustion of coal-bearing dumps is its geodynamic position, i.e. its location in the geodynamically dangerous zone (GDZ) at the boundary of the Earth crust blocks. This hypothesis is put forward on the basis of scientific ideas about the block structure of the Earth crust and the available statistical data on the location of burning dumps and is studied using computer modeling. A dump located in the area of Eastern Donbass was chosen as the object of research. The simulation results show that the penetration of air into the dump body from the mine through the GDZ, which crosses the mining zone, is possible at an excess pressure of 1000 Pa created by the main ventilation fans. The fire source appearance in the dump body causes an increase in the temperature of the dump mass and becomes a kind of trigger that "turns on" the aerodynamic connection between the dump and the environment, carried out through the GDZ. It is concluded that the establishment of an aerodynamic connection between the mine workings and the dump through the GDZ can be an important factor contributing to the endogenous fire hazard of coal-bearing dumps. The simulation results can be used in the development of projects for monitoring coal-bearing dumps and measures to combat their spontaneous combustion

Modelling of Aerodynamic Process for Coal Waste Dump Located in Geodynamically Dangerous Zone

Previously made evaluations show confinement of fire coal waste dumps to geodynamically dangerous zones which in this work are considered as borders of active blocks of the earth crust. According to the hypothesis under development, when disposing the dumps in geodynamically dangerous zones (GDZ), which have a high penetrating, aerodynamic relation of the dumps with the environment occurs, making the dumps firing possible. Firing of the dumps inflicts environmental, social and material damage. This research is aimed to study possible mechanism of gas mass transfer through GDZ into the body of dump on the base of computer modeling of aerodynamic processes. A relevant geometry model is developed, borderline conditions are proven and modeling of aerodynamic process is shown in the work. Taking into account actual data on location and characteristics of firing dumps of a region of Eastern Donbas (Rostov region, Russia) calculation are performed by means of ANSYS software. A dump located in GDZ is modeled. The GDZ is set in the model as a highly penetrating linear zone in the rock, which has a deep emplacement. The GDZ crosses mine fields and has an expression in relief of the Earth surface. Temperature of the rock within the dump may reach 420 degrees Centigrade. Petrophysical characteristics are taken into account in the model (porousness and permeability) of its main structural elements, dimensions of the dump, width of GDZ, difference of relief heights, depth of mine workings location under the dump. The results of the modeling show influence of the dump temperature, petrophysical characteristics of the model structural elements, depth of the mine openings location on aerodynamic processes within the dump mass. Operability of the model at the preset border conditions allows to deeply argue the hypothesis of the air intake into the dump body with consideration of the local geodynamics. According to the results obtained, geodynamic conditions of mining area where coal waste dumps are disposed, may be and are an important factor, which has an effect on creation conditions for spontaneous combustion of dumps and its further impact on environment