Supporting mechanism of yielding-supporting beside roadway maintained along the goaf under hard rocks

When using gob-side entry retaining on the condition of hard roof, roadside support deforms and destroys easily because the length of hanging roof is large, the roof hangs long, and the stress exerted on roadside support is large. Mechanical model for gob-side entry on the condition of hard roof was built, and stress distribution of roadside support and deformation of surrounding rocks during different movement stages were simulated. Results show that in the early movement stage, in order to release some roof stress, roadside support should have larger yieldable capacity which allows roof to have certain subsidence under the premise that the support is not destroyed severely. In the later movement stage, roadside support should have greater strength to resist the weight of hard roof and cut roof. Based on this mechanism, unequal strength support body which is combined by soft material on the top and hard material in the bottom is put forward, and the field practice demonstrates that gob-side entry retaining technology on the condition of hard roof can be better achieved by using unequal strength support body.