Study on influence rules of gas extraction drilling borehole spacing on stress superposition effect

In order to study the rules of stress superposition effect and analyze the influence on the punching coal amount by borehole spacing, according to the general situation of Jiulishan Coal Mine and the actual situation of through-bed drilling construction, a solid mechanics model was established by using simulation software COMSOL. We mainly studied the stress superposition effect under different borehole spacings when multiple boreholes are arranged, and analyzed the actual situation of punching coal amount in II₁ coal seam of Jiulishan Coal Mine. The results show that when the pre-peak area of stress concentration is superimposed, the stress value near the superimposed area increases with the decrease of hole spacing; when the post-peak area of stress concentration and the pressure relief area are superimposed, the stress values near the superimposed area decrease, but the stress values on both sides still increase; the number of boreholes can lead to a greater degree of superposition effect by affecting the number of coal disturbance, and the stress of the layout of three holes is circular distribution, and the degree of superposition effect will be weakened by increasing the force area; when drilling in the area of stress superposition, the punching coal amount of drilling is often large and instability may occur.