Physical Simulation Study on the Asymmetric Fracture Evolution of Overburden in a Deep Pillarless Longwall Panel Under Roof Cutting and Pressure Relief

This study investigates the asymmetric evolution of overburden deformation and fracture during unilateral roof cutting in a deep pillarless longwall panel. The No. 31120 working face at Suncun Coal Mine was used as the prototype for a 1:40 physical similarity model. Fracture observations, digital image correlation fields, subsidence profiles, and paired vertical-stress histories were analyzed throughout support advancement, sustained support, and support withdrawal. The maximum-subsidence region and dominant fracture boundary shifted toward the non-cutting side, whereas the cutting side developed smaller caved blocks and a shorter retained roof span. A longer cantilever-like roof segment formed on the non-cutting side and a shorter segment formed on the cutting side, accompanied by contrasting loading and unloading responses at corresponding roof levels. The combined observations show that unilateral roof cutting redirects roof fracturing and load transfer and provide an experimental basis for evaluating retained roof span, separation, and support demand near a gob-side roadway.