Study on optimization of single-layer drilling parameters based on pressure arch theory in auger drilling

In order to scientifically design the drilling layout parameters of auger drilling rigs in a certain mine, according to the stress distribution characteristics around the drilling holes, a method for determining the effective width of coal pillar between adjacent drilling holes was put forward, and the key parameters of single-layer drilling arrangement were determined. Combined with the theory of pressure arch, it is proposed that the stress concentration coefficient at the middle point of the permanently isolated coal pillar is used as the criterion to determine the rationality of the width of the permanently isolated coal pillar. The orthogonal test method was used to design nine orthogonal test schemes, and the finite element difference software was used for numerical simulation, based on the pressure arch theory to analyze the simulation results and optimize the optimal scheme. The results show that the smaller width of coal pillar between adjacent boreholes makes the originally independent pressure arch on the borehole form a pressure arch, and the key layer can effectively limit the height of the outer boundary of the pressure arch, and the permanent isolation of the coal pillar can effectively eliminate the influence of adjacent borehole groups. The proposed method for determining the effective width of coal pillars between adjacent drilling holes proposed in this paper is suitable for the design and study of mining parameters of auger drilling rig. In Scheme 9, the number of adjacent boreholes is 25, the width of coal pillars between adjacent boreholes is 1 m, and the width of permanent isolated pillar is 10 m, and the surrounding rock under the key layer is relatively stable. The ratio of the width of plastic zone in the monitoring coal pillar to the effective width is 0.4, and the stress concentration coefficient at the middle point of permanent isolation pillar is 1.382. This scheme is the best.