Research and application of precision three-dimensional drilling for stress relief and surrounding rock control in high-stress roadways

The borehole pressure relief method for high-stress roadways features simple construction, convenient operation and low equipment requirements, making it an effective technique for surrounding rock control in Guizhou Province. The precision three-dimensional pressure relief technique forms a spatially coordinated and integrated pressure relief system. According to the three-dimensional distribution of high-stress fields in surrounding rock masses, targeted pressure relief measures are designed and implemented for the roof, sidewalls and floor simultaneously. Roof pressure relief is designed to cut off high-stress transmission paths within key strata; sidewall pressure relief directly alleviates concentrated stress in adjacent rock masses; floor pressure relief restrains floor heave by diverting stress to deep or lateral zones. Statistical analysis was performed on field applications of borehole pressure relief in high-stress roadways of coal mines to assess key parameters including drilling depth, diameter and spacing, and determine their optimal ranges. The results show that pressure relief performance is highly sensitive to reasonable parameter selection. To achieve efficient stress relief, this study investigates the effects of drilling parameters on pressure relief performance and proposes the elastic spine beam theory. According to this theory, the borehole pressure relief zone acts as an elastic spine beam whose stiffness is lower than that of the surrounding elastic rock masses. Under concentrated stress, the elastic spine beam dissipates elastic energy via deformation and transfers stress peaks to the surrounding elastic zone. Excessively deep boreholes hinder the migration of high stress to the elastic zone, causing the elastic spine beam to suffer plastic failure under loading. Likewise, an overlarge borehole diameter or excessively dense borehole layout expands the cumulative plastic zone, reduces the effective area of the elastic spine beam, raises stress levels and triggers plastic deformation. This plastic deformation induces large lateral displacement and further exacerbates the deformation of roadway surrounding rock. Based on numerous field cases, a basic technical workflow for precision three-dimensional pressure relief in high-stress roadways is put forward. Field trials conducted at Shanjiaoshu Mine and Tucheng Mine in the Guizhou mining area achieved favorable surrounding rock control effects. The results verify that precision three-dimensional pressure relief is a practical, reliable and engineering-applicable method for roadway stress regulation.