Study on disaster-causing law of different types of hidden structures in deep coal seam

In the process of deep mining, the geological type of the mine is complicated. Under the condition of “three heights and one disturbance”, it is easy to cause coal and gas outburst and other coal and rock dynamic disasters near the hidden structure. In order to clarify the mechanism of dynamic disasters induced by hidden structures, taking No.8 Mine in Pingdingshan as the engineering background, the stress-strain evolution characteristics and disaster causing law of normal and reverse faults in different mining directions and their simultaneous existence are studied by numerical simulation, and the influence of different hidden structures on driving face is analyzed. The results show that when driving encounters a single fault, the stress-strain is concentrated in front of the work and inside the fault. Normal faults are more likely to produce stress concentration, and the range of stress concentration is larger. At the same driving distance, the principal strain of the reverse fault is slightly larger than that of the normal fault. With the driving distance increases, when the driving distance increases to 15 m, the stress-strain concentration area gradually coincides, and finally a stress-strain superposition area is formed in the fault area. When driving encounters multiple faults, the stress is concentrated on the structural coal in front of the working face and between the two faults. The superimposed stress-strain distribution is different in the case of normal-reverse faults and reverse-normal faults. In the case of normal-reverse faults, the superimposed stress-strain is mainly distributed near the normal faults. In the case of reverse-normal faults, the stress-strain in structural coal between the two faults also increases significantly. Near the multiple hidden structures dominated by reverse faults and reverse faults, the increase rate of strain energy is larger, which is more conducive to the accumulation of strain energy, and the risk of coal and gas outburst increases. Under the combined action of mining stress, fault structural stress and static stress in the coal rock mass, coal and gas outburst and other coal and rock dynamic disasters are eventually triggered. Multiple hidden structures are more likely to produce stress concentration than single structures, and the risk of coal and rock dynamic disaster increases.