Determination of the Spontaneous Combustion Hazardous Zone and Analysis of Influencing Factors in Bedding Boreholes of a Deep Coal Seam

Abstract

Accurately determining the spontaneous combustion zone of coal around the borehole plays an important role in preventing borehole accidents. To solve the problem of dividing the hazardous zone of spontaneous combustion in boreholes, a fully coupled model of the gas flow, coal oxidation reaction, and energy transportation is developed in this study. Taking the drainage borehole of the 24130 working face in the No. 10 Coal Mine of the Pingdingshan mining area as an example, the proposed model is used to simulate the seepage velocity field, oxygen concentration field, and temperature field of the coal around the borehole. The simulation results are found to be consistent with the field test results. Based on the simulation results, the coal around the borehole is divided into two areas in the axial direction of the borehole. The intersection of the seepage velocity u ≤ 0.004 m/s and oxygen concentration 7% ≤ C(O2) ≤ 21% are considered the “hazardous zone”, and the union of the oxygen concentration C(O2) < 7% and seepage velocity u > 0.004 m/s are considered the “safety zone”. The influences of various factors inducing spontaneous combustion of coal around the borehole on the hazardous zone are revealed by analyzing the drainage negative pressure, sealing length, and roadway temperature. The results show that reducing the drainage negative pressure and increasing the sealing length can effectively restrain the spontaneous combustion of the borehole and can also help reduce the scope of the hazardous zone of the borehole. Finally, a reasonable arrangement of the predrainage period in the appropriate season can also effectively inhibit the spontaneous combustion of coal around boreholes.

Risk identification of coal spontaneous combustion based on COWA modified G1 combination weighting cloud model

“…When the thickness of residual coal is large, the contact between residual coal and oxygen increases, and the risk of spontaneous combustion of coal is higher 18 . The faster the working face advancing, the shorter the oxidation zone retention time, and the smaller the risk of spontaneous combustion 19 . Ventilation management defects affect the air leakage in goaf.…”

Prevention Technology of Coal Spontaneous Combustion Induced by Gas Drainage in Deep Coal Seam Mining

“…Coal spontaneous combustion occurs under three conditions: oxygen concentration, wind speed, and time [32][33][34][35]. Only when the ventilation and oxygen supply conditions are continuous and stable for a period of time, enough to combine the coal with sufficient oxygen, the oxidation process is fully carried out and the coal body can spontaneously ignite when a certain amount of heat is accumulated [36,37].…”

“…The length of roadway shotcrete affects the scope of the dangerous area around the borehole, so the method of combining numerical simulation and engineering is used to study the law of the influence of shotcrete on the oxygen concentration, fluid velocity, and the scope of the dangerous area around the borehole. According to the spontaneous combustion of the coal seam (Jia et al, 2021)…”

Numerical Simulation of Coal Spontaneous Combustion around a Borehole Induced by Negative Pressure Gas Drainage

“…Spontaneous combustion mainly occurs around the borehole; therefore, the coal around a single borehole is selected as the main calculation area. The main parameters of this model (Table 1) are from experimental results and references [30,35]. Based on the actual situation, the initial and boundary conditions are listed in Table 1.…”