82 / 2021-11-30 17:13:34

Theoretical identification method of “vertical three zones” based on soft-hard overburden composite structure and its engineering application

vertical three zones;soft-hard overburden composite structure;key stratum theory;theoretical identification method

Resource Development and Utilization > 11. Mine Water Hazard, Pollution Prevention and Control, and Utilization of Mine Water Resources

Coal mining induces overburden damage which results in the formation of “three vertical zones” (i.e., the collapse zone, the fracture zone and the bending subsidence zone). The overburden generally migrates in the form of a rock group which comprises both lower hard rock that plays a bearing role and the upper soft rock. According to the key stratum theory and the fracture mechanics analysis, whether the broken rock strata can form a masonry beam structure and whether rock strata are broken are the key to distinguishing between the collapse zone and the fracture zone and between the fracture zone and the bending subsidence zone. In view of the above fact, in this study, the mechanical model under the critical condition of hard rock and soft rock breakage was established. Besides, the stability condition for the broken rock strata to form a masonry beam structure, as well as the bending deformation formula of soft rock and hard rock based on deflection, was deduced. Furthermore, a new theoretical identification method of “vertical three zones” based on soft-hard overburden composite structure was proposed.

With reference to the specific mining geological conditions of the JX15101 longwall mining face, the results obtained by the proposed theoretical identification method, the numerical simulation results and the on-site measurement data were comparatively analyzed by means of borehole television observation, leaking liquid measurement and numerical simulation. Ultimately, the comparison successfully verified rationality and practicability of the proposed theoretical identification method.