Double-Layer Flexible Thick Anchor Technology for Surrounding Rock Control During Gob-Side Entry Driving in Deep Coal Seam Mining with Large Heights

To address the challenge of surrounding rock control in deep gob-side entry driving, the return airway of the 20203 working face of the Dahaize Coal Mine was taken as the engineering background. The stress, deformation and plastic zone evolution characteristics of the surrounding rock of the gob-side entry were studied through theoretical analysis, numerical simulation and field tests, and the surrounding rock control mechanism and the double-layer flexible thick anchor control technology were proposed. The results show that under the influence of the adjacent gob, the peak compressive stress of the gob-side entry is transferred to the solid coal side, and tensile stress areas are generated on the roof; shear failure is the main failure pattern of the surrounding rock in the gob-side entry, which is characterized by significantly asymmetric deformation. Based on the displacement failure characteristics of the surrounding rock zones, a double-layer flexible thick anchorage structure was constructed. The anchorage depth of the first basic support exceeds the critical thickness of the shallow fractured surrounding rock zone, forming a thick load-bearing layer for the roadway surrounding rock; the anchorage depth of the secondary reinforced support extends into the stable rock mass, enhancing the bearing capacity of the anchored body and the roadway surrounding rock. The results of numerical simulation show that after adopting a double-layer flexible thick anchor support, the average deformation of the roof decreases by 48.81%, and the range of the tensile stress zone and plastic zone is significantly reduced. In engineering applications, the average deformation of the roadway roof was 42.58 mm, the two-end convergence was 0–2 mm, the roof separation value was controlled within 0–30 mm, and the rock strata within 0–5.0 m remained intact. This technology effectively suppresses the large deformation of the surrounding rock in deep gob-side entry, providing an innovative strategy for roadway stability control under comparable geological and mining conditions.