Abstract:
By introducing Concrete Damage Model yield criterion in Abaqus software, the damage state of coal pillar in the process of drilling and mining was investigated. Taking the 81117 working face of Pingshu Coal Mine as an example, Fluent software was used to analyze the influence of the gas flow state in goaf, the spacing of boreholes, the quantity of boreholes and the pumping capacity on the gas control effect. The results show that there is no obvious damage to coal pillar during drilling and excavation. In the process of coal winning, there is a tendency of communication between the roof of the roadway and the high stress area of the surrounding rock of the borehole, so the supporting strength of the roadway near the borehole should be strengthened in advance. When the number of boreholes is 4, the optimal hole spacing is 30 m. The increase of borehole spacing will reduce the efficiency of gas extraction while improving the extraction range. However, the quantity of extraction boreholes should not be more than 4, and continuing to increase the quantity of boreholes will lead to a mismatch between the construction cost and extraction efficiency. The upper limit of effective pumping capacity is 30 m
3/min, and the optimal pumping capacity is 20 m
3/min. Before the large-diameter drilling and extraction technology was adopted, the gas concentration in the upper corner was 0.60% to 1.05%, and after the adoption of this technology, it was reduced to 0.3% to 0.8%, which verified the reliability of the technology.