Numerical simulation study on the optimal parameters for destressing boreholes in the two ribs of excavation roadways in extra-thick coal seam

ZHAI Xinxian; REN Zhu'an; FANG Jianchang; ZHANG Zhiyong; LU Defang; ZHAO Xiaofan; GUO Zhaoyang

doi:10.16186/j.cnki.1673-9787.2023030035

Abstract：At present,borehole destressing technology is one of the main measures to prevent coal bump during roadway excavation in coal mines.Objectives Borehole layout and parameters determine the destressing effect.Methods Based on the geological and mining conditions of the roadway in the fully mechanized caving face of Gengcun Coal Mine,the numerical calculation was used to study the stress cloud diagram of the surrounding rock of the roadway and the vertical stress distribution characteristics of the two ribs of the roadway,while the destressing boreholes were arranged with different borehole depths,diameters and row spacings in single-row and with different double row spacings in double-row.Results The results are as follows.(1)While the destressing boreholes are arranged in a single row,with the increase of borehole depth and diameter,the higher stress area of the two ribs of the roadway gradually shifts to the deep surrounding rocks,but the shal-low surrounding rock of the two ribs of the roadway is in the lower stress area.(2)When the depth and diam-eter of the boreholes reach a certain value,the abutment pressure curve of the two ribs of roadway is changed from single peak to double peak one,and the shallow surrounding rock of the two ribs is in a critical destressing state.As the borehole depth and diameter continue to increase,the two ribs of roadway are in a state of excessive destressing.(3)By using the transfer amount ∆L of the high stress zone of the two ribs of the roadway to the deep surrounding rock and the ratio η of the distances between the peak stress and the surface of the roadway after its destressing and without destressing boreholes,the two quantitative indexes are used to represent the critical destressing and excessive destressing states,and the reasonable parameters of the destressing boreholes are determined.It is the advanced destressing boreholes and secondary supporting with bolting and cable anchor plus 36U type retractable metal support,that was implemented in the roadway of longwall caving face 13230 in Gengcun Coal Mine,the implementation effect of deep borehole destressing and anti-impact on the two ribs of the roadway is remarkable.Conclusions The conclusions have reference and guiding significance for the prevention of coal bumps during the excavation of roadway in coal mine.