Study on Stress Evolution and Surface Subsidence of Phased Filling and Mining Technology

To study the characteristics of stress evolution and surface subsidence of filling mining technology, the numerical simulation and field measurement methods were applied for analysis. The results showed that in the first stage of mining, the coal pillar is the main support body, while the filling body is the passive support body, which mainly plays the role of stress transfer, as the roof subsidence begins to gradually bear the load, the filling body and the coal pillar form a unified support body, which improves the supporting capacity mutually, in this stage, the roof and the surface only slightly sink; during mining in stage 2, the stress evolution process is similar to that in stage 1, the maximum vertical stress of coal pillar is 22 MPa, and the maximum vertical stress of backfill is 12.0 MPa. However, the roof and surface subsidence is large, and the subsidence in stage 2 accounts for 83.2% of the total subsidence. The measured results are consistent with the simulated results. Compared with caving method, the surface subsidence is reduced by 92%.