Zonal Disintegration Characteristics of Roadway Roof Under Strong Mining Conditions and Mechanism of Thick Anchored and Trans-boundary Supporting

Under strong mining stress, the coal seam roadway is often troubled with engineering problems, such as intensive deformation of its surrounding rock or the instability and sinking of its bearing structure. By analyzing the mechanism of roadway deformation and disintegration under strong mining conditions, this paper introduces the principle of thick anchored and trans-boundary (TATB) supporting as well as its engineering application and validation under such conditions. To begin with, field surveys and similar simulation experiments show that the process of roadway surrounding rock deformation has obvious stage deformation characteristics and zonal disintegration characteristics, and that the key to support is to restrain the initial deformation and bed separation of surrounding rock. Second, this paper puts forward the mechanism of TATB supporting based on the foresaid characteristics, indicating that the scope of anchoring support must include the critical anchorage length with the anchoring end embedded in the elastic rock body deep in overlying strata when the roadway is under strong mining conditions. Third, a technical support plan is proposed, and an industrial experiment is conducted, achieving good effect according to the data from field monitoring. In addition, we discussed the relationship between the stage deformation characteristics and zonal disintegration characteristics as well as the improvement of the zonal disintegration characteristics by the TATB supporting. During the initial stage of deformation, displacement is mainly related to the dilatancy of rock mass caused by released elastic strain energy, while during the late stage, displacement is mainly caused by the rigid displacement during the breaking of the layered roof and its re-stabilization. Moreover, the formation and upward extension of longitudinal cracks are dominant in the staged deformation of surrounding rock and the zonal disintegration process. In addition, the TATB supporting prevents the upward circulation of the zonal disintegration in roof strata and thereafter restrains major deformation of surrounding rock by limiting the development of longitudinal cracks. This study can provide a reference for maintaining roadway roof stability under similar conditions.