Impact of controllable parameters in hydraulic slotting on stress relief effects around coal seam

Hydraulic slotting technology has broad application prospects in coal seam gas management. Using the FLAC3D finite difference software and an evolution model considering plastic damage, the unloading damage characteristics under unequal pressure conditions during the hydraulic slotting process are simulated. The results show that factors such as borehole diameter, drilling depth, slot radius, and borehole spacing significantly impact the unloading damage effect. Specifically, increasing the borehole diameter, drilling depth, and slot radius expands the unloading damage area, forming “butterfly-shaped” or “elliptical” plastic zones. Reducing the spacing between parallel slots causes overlapping unloading damage in the coal body between adjacent slots, further enhancing the stress reduction effect. The “high–low–high” pattern of parallel slots effectively supplements and strengthens the weak stress unloading zones, better fracturing the coal seam. Field testing confirms that hydraulic slotting significantly increases borehole radius and gas extraction. These results validate simulations and enhance coalbed methane extraction's safety and efficiency, providing robust guidance for optimizing parameters.