Coal Spontaneous Combustion In Goaf Research Articles

Risk field assessment of longwall working face by the double-sided roof cutting along the gob

In order to study the mechanism of the dual side roof cutting technology on the composite disaster of gas and coal spontaneous combustion in goaf, a model for the evolution of porosity and permeability in the dual side roof cutting working face was constructed. The location of the occurrence of the compound disaster of gas explosion and coal spontaneous combustion under the double-sided roof cutting mode was studied, and the sensitivity of the evolution pattern of the compound disaster area to the amount of air supply and gas gush was summarized. The results indicate that the top cutting pressure relief technology significantly reduces the permeability of porous media, and the sensitivity of the goaf on the intake side to airflow disturbances is significantly reduced. As the volume of air supply increases, the distance between the gas explosion risk area and the coal spontaneous combustion risk area gradually decreases, and the probability of composite disaster areas is 0. The increase of air supply and gas emission makes the gas concentration in the middle and deep goaf increase in an exponential function, and the width of the gas explosion risk area increases gradually. When the outflow reaches 40 ​m3/min, there is no composite disaster zone, indicating that the rapid increase in outflow inhibits the occurrence of composite disasters.

Study on the Cause of Hypoxia in the Corner of Return Air of Shallow Buried Flammable Coal Seam Group Mining Face and the Coordinated Prevention and Control of Coal Spontaneous Combustion

Coal is the main energy source in China, and spontaneous combustion of coal is one of the main disasters in coal mines. Fully mechanized caving top coal mining technology is widely used in coal mines. Under the comprehensive action of multiple factors, gas generated by coal oxidation and low oxygen gas in goaf is easy to rush to working face, resulting in lower oxygen concentration in upper corner and exceeding harmful gas concentration. It seriously threatens the health of underground workers and the normal operation of production. If the oxygen concentration in the upper corner is changed, it is bound to cause the change of the oxygen concentration in the goaf and aggravate the threat of spontaneous combustion of coal in the goaf. In order to solve the double threat of low oxygen in upper corner and coal spontaneous combustion in goaf, based on Coulomb model, this paper uses command flow to conduct numerical simulation tests on the failure law of overlying strata, and obtains the influence of mining of the lower 1 coal seam and the lower 5 coal seam on the overlying strata subsidence and surface penetration. Based on the comprehensive consideration of atmospheric pressure, ore pressure activity, external air leakage and other factors, the mixed model of the source and emission of low oxygen gas in goaf was established, and the formation mechanism of low oxygen problem in the corner of return air of working face was defined. The use of pressure air belt to deal with low oxygen in return air corner is proposed creatively. The comprehensive fire prevention measures such as corner plugging, nitrogen injection and grouting are used to inhibit the oxidation of the left coal and the influx of low oxygen gas to the corner in the goaf, so as to achieve the goal of collaborative prevention and control of low oxygen in the corner of return air and coal spontaneous combustion. The research results have important reference significance for the mine with the risk of spontaneous combustion or the problem of low oxygen in the return air corner.

Experimental Study on Influencing Factors and Thermal Effects of CO2 Adsorption by Coal.

The utilization of CO2 is extremely important to solve the environmental problems and coal spontaneous combustion in goaf. There are three kinds of CO2 utilization in goaf: adsorption, diffusion, and seepage. Since adsorption will consume CO2 in goaf, the optimization of CO2 injection amount is very critical. A self-developed adsorption experimental device was used to determine the CO2 adsorption capacity of three different particle sizes of lignite coal samples at 30-60 °C and 0.1-0.7 MPa. The factors affecting CO2 adsorption by coal and its thermal effect were studied. In the coal and CO2 system, the CO2 adsorption characteristic curve is not affected by temperature, but there are differences in that with different particle sizes. The adsorption capacity increases with the increase of pressure, while it decreases with the increase of temperature and particle size. Under atmospheric pressure, the adsorption capacity of coal is a logistic function relationship with temperature. Furthermore, the average adsorption heat of CO2 on lignite shows that the interaction force between CO2 molecules has a stronger effect on CO2 adsorption than the effect of heterogeneity and anisotropy on the coal surface. Finally, the existing gas injection equation is improved theoretically with CO2 dissipation, which provides a new idea for the work of CO2 prevention and fire suppression in goaf.

Study on the Coupling Characteristics of Infrasound–Temperature–Gas in the Process of Coal Spontaneous Combustion and a New Early Warning Method

ABSTRACT The phenomenon of coal spontaneous combustion poses a serious threat to mine safety, and monitoring and warning of coal spontaneous combustion has become an important issue that needs to be urgently addressed in coal mines. The current monitoring and early warning methods for coal spontaneous combustion have their limitations, and a single indicator cannot accurately mark the degree of coal spontaneous combustion danger inside the goaf. Therefore, this article proposes a new method for monitoring coal spontaneous combustion through infrasound waves. Infrasound waves have advantages such as low attenuation and long transmission distance. However, current research on monitoring and warning coal spontaneous combustion in goaf through infrasound waves is not yet complete, and there is a lack of research on the characteristics of infrasound signal changes during coal spontaneous combustion. Based on this, the article first tested the characteristic temperature and release changes of indicator gases (CO, C2H4) through thermogravimetric experiments and coal oxidation and heating experiments. Then, the generation and variation of infrasonic signals during coal spontaneous combustion (CSC) was studied and analyzed using a self-designed CSC infrasonic testing system. The results showed that obvious infrasound signals could be generated during the CSC process, there is a good mapping relationship between signals and temperature. Furthermore, the analysis revealed the inherent relationship between the infrasonic signal, temperature, and indicator gas of coal at different oxidation stages. The research in this article has promoted the use of infrasound waves for temperature inversion and promoted the development of multi-parameter analysis and early warning of CSC, which is of great significance for the field of CSC monitoring.

N2 Inhibition Characteristics of Coal Spontaneous Combustion in Goaf: Experimental Study and Numerical Analysis

ABSTRACT To investigate the inhibition characteristics of coal spontaneous combustion in goaf under different nitrogen injection conditions, the oxidation and the heat release characteristics of coal bodies with easy spontaneous combustion were characterized by using adiabatic oxidation experiment. A comparative study on the evolution of the coal spontaneous combustion risk zone (CSCZ) in goaf was carried out by using numerical simulation. The results indicate that the oxygen consumption rate of coal bodies with the rise of temperature in a power function. The exothermic characteristics of coal decrease with the increase of N2 addition. The location and rate of N2 injection restrict the expansion process of CSCZ, which makes the maximum width of CSCZ shrink, the oxygen attenuation rate, N2 diffusion intensity and inerting area increase. When the N2 injection position is 40 m away from the working face and the N2 injection rate is 450 m3/min, the critical ideal value of inhibition coal spontaneous combustion can be achieved.

Study on Multifield Migration and Evolution Law of the Oxidation Heating Process of Coal Spontaneous Combustion in Dynamic Goaf.

To study the dynamic evolution law of the oxidation heating process of coal spontaneous combustion in the goaf during the advancing process of the working face, a dynamic model of oxidation heating of coal spontaneous combustion in the goaf was established on the basis of deformed geometry. Through numerical simulation research, the evolution and migration laws of seepage field, oxygen concentration field, temperature field, and high-temperature area of coal spontaneous combustion in the goaf during the advancement of the working face was obtained. The results indicate that the distribution of the bulking coefficient, porosity, and permeability of the falling coal and rock mass in the goaf is nonuniform. They are relatively large in the area near the working face and the inlet and return airway and remain relatively unchanged with the advancement of the working face, but they are constantly decreasing in the location of the gob in the middle and deep. The oxygen concentration in the goaf presents an asymmetrical distribution. The oxygen concentration distribution area on the inlet side is wider than that on the return air side. At the same depth of the goaf, the oxygen concentration gradually decreases from the inlet side to the return air side; after the advancement distance exceeds 200 m, the air leakage in the goaf basically disappears, and the oxygen concentration decreases to zero. The high-temperature area of coal spontaneous combustion oxidation in the goaf was mainly concentrated on the air inlet side and extended toward the return air side. The advancing speed has a significant effect on the oxidation heating process of coal spontaneous combustion in the dynamic goaf. Under the same propulsion distance, when the advancing speed is 6 m/day, the highest temperature in the goaf is about 40 °C, and when the advancing speed is 2 m/day, the highest temperature in the goaf is as high as 120 °C. The smaller the advancing speed, the higher the heating rate of the goaf and the closer the high-temperature area to the working surface. The higher the advancing speed, the lower the temperature of the high-temperature point of the goaf and the greater the depth of the high-temperature point of the high temperature area; when the advancing speed is 2 m/day, the highest temperature point in the goaf is 70 m away from the working face, whereas when the advancing speed is 6 m/day, it reaches 174.6 m.

Air Leakage Law and Prevention Technology of Coal Spontaneous Combustion in the Goaf of “Isolated Island” Fully Mechanized Caving Face

ABSTRACT The coal pillar along the goaf of the completely mechanized caving face of “Isolated Island” is severely damaged, with complex air leakage and a high risk of coal spontaneous combustion. In order to research the law of goaf air leakage in “Isolated Island” working face and effectively control the hidden threat of coal spontaneous combustion in goaf, it is necessary to investigate the goaf air leakage law. In this work, the 3302 “Isolated Island” entirely mechanized caving face of Jining No. 2 Coal Mine in Shandong province, China, served as an example. SF6 tracer gas air leakage measurement was utilized to identify the air leaking route in the goaf. In conjunction with the numerical modeling, the air leakage route surrounding the goaf was evaluated to establish the coal spontaneous combustion risk region, and the targeted prevention and controlled ways of coal spontaneous combustion were proposed. The results indicated that the primary source of air leakage was the seepage of air flow through the working face to the rear goaf and the diffusion to the adjacent goaf through the broken coal pillar. The risk area for coal spontaneous combustion was 40–80 m behind the rear goaf and 50 m within the coal pillar of the adjacent goaf. Regarding this region, the comprehensive prevention and control strategies of plugging and oxygen reduction, inerting and cooling, monitoring and forecasting were proposed. In addition, the fire prevention and extinguishing system combining slurry spraying, sodium silicate, and liquid CO2 injection was designed at both ends of the 3302 track and haulage roads. Using field measurements during the working face mining process, the corresponding methods for reducing the CO volume fraction in 3302 return air roadway and air return corner effectively prevented and controlled the hidden danger of coal spontaneous combustion in the goaf and ensured the safety of working face mining. This research developed a new technology for the prevention and management of coal spontaneous combustion in the goaf of the “Isolated Island” working face.

Analysis of the Coal Spontaneous Combustion Risk Space Evolution in the Goaf Under Ventilation and Extraction Coupling

ABSTRACT The risk of coal spontaneous combustion in goaf is one of the disasters in coal mining, ventilation and extraction often aggravate air leakage from the goaf. Due to the unclear rule of expansion law and air leakage, the risk space for coal spontaneous combustion continues to occur. To investigate the influence of ventilation and extraction on the evolution of the risk space of coal spontaneous combustion (CSC) in goaf, further reveal the characteristics of air leakage and extraction in goaf and obtain the expansion law of CSC risk space. A three-dimensional model of goaf under surface drilling and gas extraction was developed. Using FLUENT numerical simulation software, taking a coal mine in Anhui Province, this study analyzes the influence factors, evolution law, and influence characteristics of CSC through field observations and numerical simulation. The research indicates that ventilation keeps the risk space of CSC expanding. The extraction of single drilling showed a local space expansion, while the extraction of double drilling shows the overall space expansion of the goaf. The air leakage flow path in goaf, air flow velocity vector in working face, gas concentration loss, and gas extraction characteristic parameters are determined. The loss of air leakage along the working surface meets four-stage: “strong in – flow - mixed flow – steady inflow – sudden outflow.” It can be determined that the extraction intensity of single drilling should be greater than 34.8 m3/min, and the double drilling should be greater than 18.7 m3/min. The relationship between the coupling influence of ventilation and extraction and the expansion law of CSC risk space is determined, and the maximum risk space width of CSC can be predicted. The research results are of guiding significance for CSC prevention and gas efficient extraction.

Optimal Parameters of Gas Drainage and Carbon Dioxide Inerting Technology and Its Application in a High Gassy and Spontaneous Combustion Mine.

In the process of coupling disaster prevention and control of gas and coal spontaneous combustion in goaf, there is a great contradiction between the gas drainage and carbon dioxide inerting technology. The key performance indexes are put forward to solve the coupling disaster, such as the air quantity of the intake airway (A), the gas drainage rate (B), the carbon dioxide injection rate (C), and the injection depth (D). Using the numerical simulation method and the orthogonal test of four factors and three levels, we establish the coupling disaster model of the no. 7436 working face in the Kongzhuang coal mine. Using a combination of the relative membership degree method and range analysis, the optimal level of each factor is determined, which is AIIBIIICIIDII. Furthermore, the distribution law of the airflow field is obtained under the conditions of different gas drainage rates and carbon dioxide injection rates. The results show that the gas concentration decreases with an increase in gas drainage in the upper corner, but it has little impact on the width of the oxidation zone. The gas concentration can be reduced to 1%, while the gas drainage rate is higher than 35 m3/min. With an increase in gas injection rate, the carbon dioxide emission rate increases in the upper corner, but the width of the oxidation zone decreases. Also, the gas injection rate should be less than 800 m3/h. Moreover, with an increase in injection time in the upper corner during the injection process, the carbon dioxide and gas concentrations increase, and the maximum carbon dioxide concentration is 1.3%, and the maximum gas concentration is 0.42%, which is consistent with the results of numerical simulations.

Preparation of superabsorbent lignin-based composite inhibitor and research on its prevention and control characteristics of coal spontaneous combustion

ABSTRACT With the potential safety hazard of coal spontaneous combustion becomes more and more serious, in order to solve the problems of low water absorption rate and high cost of hydrogel inhibitor, in this study, a superabsorbent lignin-based composite inhibitor (SAP + SLS + Ben) was prepared. The water absorption/retention rate, micromorphology, inhibition capacity, air-leakage blocking efficiency and fire-extinguishing performance of SAP + SLS + Ben were studied. Results have revealed that: SAP + SLS + Ben had excellent water absorption/retention capacity; SEM images revealed that sodium lignosulfonate (SLS) and bentonite (Ben) provided the structural basis for the high water absorption/retention of SAP + SLS + Ben; Compared with SAP, SAP + SLS + Ben could effectively inhibit the oxidation of reactive functional groups in coal, and the amount of CO released from coal treated with SAP + SLS + Ben was significantly reduced at high temperature; The air-leakage blocking and fire-extinguishing experiments showed that SAP + SLS + Ben had good filling and blocking performance, and could effectively reduce the temperature of coal spontaneous combustion and prevent the re-ignition of coal. Hence, SAP + SLS + Ben had ideal physical and chemical inhibition properties, which could effectively prevent coal spontaneous combustion in goaf.

Risk identification of coal spontaneous combustion in goaf based on variable weight grey target model

ABSTRACT Accurately determining the risk level of coal spontaneous combustion (CSC) in goaf is very important for coal mine safety production. In this paper, bituminous coal in Shanjiaoshu Coal Mine (SJS) was used as the research object to conduct a simulated spontaneous combustion experiment of coal with programmed heating. The results show that according to the characteristic temperature of CSC combined with the Graham R2 coefficient and the degree of spontaneous combustion and oxidation, the risk level of CSC in SJS Coal Mine is classified into four risk levels: low risk, general risk, greater risk, and major risk. Based on the grey target theory and grey entropy correlation analysis method, the equilibrium function is introduced to determine the variable weight of evaluation indexes and the risk grade judgment method of CSC in goaf. Based on the variable weight grey target model is established. The bull’s-eye distance corresponding to each risk level were 0 ~ 0.0052, 0.0052 ~ 0.1455, 0.1455 ~ 0.9554, and >0.9554, respectively. The verification results of the model based on the data of 6 groups of 12 measuring points of the beam tube monitoring system in SJS are consistent with the actual risk level.

Measurement and Numerical Simulation of Coal Spontaneous Combustion in Goaf under Y-type Ventilation Mode.

In the process of advancing the working face, the temperature rise and oxidation characteristics of residual coal in goaf and the prediction of index gas are of great significance to mine fire prevention and safety production. Based on the coal spontaneous combustion test, the oxygen consumption and heat release characteristics of coal spontaneous combustion were analyzed by taking coal samples at the working face and carrying out temperature-programmed experiments in the laboratory. The characteristic temperature and index gas of coal spontaneous combustion were determined as the judgment bases of “three zones” of spontaneous combustion in goaf, and the influencing factors of coal spontaneous combustion in goaf under Y-type ventilation were analyzed. Based on the test results, the changes of gas composition in goaf during the advancing of the W1310 working face were monitored. According to the actual situation of the W1310 working face in the Gaohe energy mine of Lu’an group, the multifield three-dimensional numerical simulation calculation and analysis of gas composition in goaf were carried out, and the distribution of oxygen concentration field in goaf under different air volume ratios of machine roadway and air roadway was studied. Through the analysis of the parameters of porous media in the goaf, combined with the actual situation, the user-defined function was compiled for the key parameters such as porosity, viscous resistance coefficient, and inertial resistance coefficient of porous media in the goaf. The three-dimensional seepage field, gas concentration field, oxygen concentration field, and pressure field of the gas components in goaf during the advancement of the goaf working face were simulated. The comparison of the numerical simulation results with the field-measured results shows good agreement. In order to consider safety, the numerical simulation results with a wide oxidation temperature rise zone are used for linear regression, and the regression equation is used to dynamically determine the O2 concentration at a point away from the goaf and to determine the “three-zone” state of the point, which is of great significance to guide the progress of the working face and safe production.

Experimental Study on Gas Migration Laws at Return Air Side of Goaf under High-Temperature Conditions

ABSTRACT In recent years, accidents of gas explosions caused by spontaneous combustion of coal have occurred from time to time. A goaf simulation experiment table was self-built to explore the influence of coal spontaneous combustion in goaf on the gas migration laws. Specifically, the gas migration laws at the return air side of goaf with or without high-temperature points at the wind velocity of 0.2, 0.6, and 1.0 m/s on the working face were analyzed. Results showed that, given the high-temperature points at the return air side, the gas concentration close to the high-temperature zone was obviously increased, the contour line of gas concentration was bent at high-temperature points, the quantity of dangerous gas explosion zone was also increased compared with that at normal temperature, and the variation amplitude of gas concentration was reduced with the increase in the distance of vertical direction from high-temperature point. The study results provide an essential experimental basis for the gas control of highly gassy coal seams susceptible to spontaneous combustion, and they have certain reference values in practical production.

Experimental investigation on microstructure evolution and spontaneous combustion properties of aerobic heated coal

Since coal oxidation and heat accumulation are prerequisites for coal spontaneous combustion, it is of great significance to study the characteristics of coal oxidation and heat accumulation to grasp characteristics of spontaneous combustion of residual coal and to locate the area with coal spontaneous combustion in goaf. In this study, three types of lignite and bituminous coal with a strong spontaneous combustion tendency were selected to prepare raw coal samples and aerobic heated coal samples. Then ultimate and proximate test, core pore and surface area test, SEM test, TG test, FTIR test and temperature-programmed test were undertaken, respectively. After coal undergoes aerobic heated progress, its surface micro-cracks, internal pore volume and specific surface area surge, and the active functional groups vary significantly; the contents of C and H fall, and that of O rises. These changes are conducive to coal oxidation. The temperatures corresponding to the first peak points in the DTG curves for the aerobic heated coal samples are lower than those for the raw coal samples, which indicates that the aerobic heated coal samples enter the self-oxidation acceleration stage earlier. Besides, according to the results of the temperature-programmed experiment, the cross-point temperatures of CO generation for the aerobic heated coal samples and the raw coal samples are 91 °C, 82 °C and 76 °C, respectively. A comprehensive analysis discloses that the aerobic heated coal samples are more likely to combust spontaneously in the initial stage of oxidation and to generate more CO. The heat dissipation zone, oxidation zone and suffocation zone were divided by monitoring the oxygen concentration changes in goaf at different stages on 5–20101 working face. It is determined that the oxidation zone of the goaf is 71–152 m on the inlet side and 59–128 m on the return side.

Experimental study to assess the explosion hazard of CH4/coal dust mixtures induced by high-temperature source surface

The explosion accident caused by the spontaneous combustion surface of coal after the coal dust is rolled up by the gas gushing from the goal seriously threatens the safety of coal coal mining. Based on this hazard, self-developed gas explosion equipment is used to detonate the CH4/coal dust mixture by high-temperature source. The process and mechanism of gas/coal dust explosion induced by coal spontaneous combustion in goaf were simulated, and its risk was evaluated. It is of great significance to understand the initiation mechanism of gas-solid mixture through coal spontaneous combustion in goaf. The results show that the explosion pressure (Pgd), explosion temperature (Tgd), rate of pressure rise ((dP/dt)gd), and explosion index (K) of CH4/coal dust mixtures are closely related to the temperature of high-temperature source and volatile content. The role of coal dust volatiles in homogeneous and nonhomogeneous reactions was revealed. Combined with three explosion parameters (Pgd, Tgd, K), the most dangerous explosion combination concentration of the selected CH4/coal dust mixture is (9.5 %, 500 g/m3), (9.5 %, 400 g/m3), and (8.5 %, 500 g/m3) at 1073 K ignition temperature. The involvement of coal dust leads to a lower explosion limit for CH4/air. The Jiang model has better applicability to the prediction of lower explosion limits for CH4/coal dust mixtures induced by the high-temperature source surface.

Study on Multi-field Evolution and Influencing Factors of Coal Spontaneous Combustion in Goaf

ABSTRACT The coupled disaster of coal spontaneous combustion and gas explosion in the goaf threatens coal mine safety production. In order to further study the mechanism of coupled disasters and provide theoretical basis for disaster prevention and control, the multi-field evolutions and the key influencing factors of coal spontaneous combustion within methane gas condition of coal mine goaf had been investigated based on the special designed hot experimental platform and numerical simulations. Results show that the leakages of ventilation air into the goaf is positively related to the intensity of coal spontaneous combustion, but that is negatively related to the ranges of methane accumulations in the goaf. During the early stage of coal spontaneous combustion, the distributions of oxygen and methane in the goaf is less affected by the temperatures. When the temperature of coal spontaneous combustion exceeds 200°C, the oxygen-poor area, methane accumulation areas and a banded high-temperature distributions area in the non-spontaneous combustion areas would be clearly formed in the goaf. The changes of gas density in the goaf indicates that coal spontaneous combustion temperature in the goaf is another important factor influencing the change of gas density and gas accumulations, in addition to the ventilation air leakages.

Experimental study on the mechanism of radon exhalation during coal spontaneous combustion in goaf

There is a good positive correlation between the high-temperature environment formed by coal spontaneous combustion in goaf and the radon exhalation in coal. The higher the temperature is, the greater the radon exhalation will be. Increasing concentrations of released radon gas will accumulate in an enclosed goaf and ultimately migrate upwards to form a radon anomaly on the ground surface. Based on this principle, the surface-based radon detection method can determine the location of underground hidden heat sources by detecting high-concentration radon areas on the ground. At present, the surface-based radon detection method has been applied in multiple fire zones as an effective technique. However, the research on the mechanism of radon exhalation during coal spontaneous combustion is insufficient, which severely restricts the detection accuracy of heat source locations of coal spontaneous combustion. In this study, radon exhalation from coal samples with different degrees of metamorphism (lignite, long-flame coal, coking coal and lean coal) at different temperatures was measured, and six main factors affecting radon exhalation (moisture, specific surface area, crack development, minerals, temperature, and gas production) were further explored. The experimental results show that with the increase of temperature, the radon exhalation from coal samples increases first and then decreases. The dissolution of radon in water and the adsorption and closure of radon in capillary pores are the main existing ways of radon in coal. When the temperature rises, the radon dispersion caused by pore water evaporation and the radon migration in cracks and pores caused by coal pyrolysis are the main reasons for the significant increase of radon exhalation.

Numerical simulation study on the influence of surface air leakage in shallow thick coal seam on coal spontaneous combustion in goaf

Numerical simulation study on the influence of surface air leakage in shallow thick coal seam on coal spontaneous combustion in goaf

Prediction method of coal mine goaf temperature and its practical application

Spontaneous combustion of coal seams in goaf seriously threatens the development of the coal mining industry. The prediction of goaf temperature is of great significance for mine disaster prevention. Based on the energy conservation equation of floating coal in goaf, the analytical solution of the steady-state temperature field in goaf is derived in this paper, and the temperature of goaf can be calculated simply through a series of physical and chemical parameters. This method is applied to Kaida Coal Mine to calculate the temperature of goaf at the return air side of 46205 working face. The results show that although there is some error between the calculated value and the measured value of the temperature in goaf, the predicted results can reflect the change rule of the temperature in goaf, and provide some guidance for the prevention and control of coal spontaneous combustion in goaf. With the increase of buried depth, the floating coal temperature rises first and then decreases. It is estimated that the maximum temperature of goaf is 27.11 °C, which is located 25m deep in goaf.

Dynamic evolution of negative pressure impact of cross-cut on oxygen concentration field in coal mine Goaf

For further understanding the coal spontaneous combustion in goaf, the dynamic evolution of the oxygen concentration field influenced by the condition of negative pressure of cross-cut were analyzed. Based on the on-site testing results, the range of the oxidation zone on the headentry and tailentry side is determined as 30 ~ 75 m and 15 ~ 65 m respectively. This paper adopts a new method called “fixed grid, dynamic attribute” to dynamically describe the spatial change of goaf caused by working face advancing. The validated model which developed by field measured data is used to study the dynamic evolution of negative pressure impact of cross-cut on oxygen concentration field in goaf. The results demonstrate that when the cross-cut is located at different positions of three zones of coal spontaneous combustion, the negative pressure of the cross-cut has different impact rules on the distribution of oxygen concentration field. The results are hopeful for providing effective guidance for coal mine fire prevention in goaf.