Study on failure law and stability control of overlying room coal pillar in shallow buried close distance coal seams mining

In order to study the instability and failure issues of overlying room coal pillar in shallow buried and close distance coal seams, and put forward the control method for coal pillar stability, the method of combining the mechanical properties test experiment of filing material and FLAC3D numerical simulation was used. The experimental investigation shows that when the pressure of compaction test reaches 15 MPa, the aeolian sand filling material will be basically dense; the mechanical properties test of aeolian sand-loess mixed material indicates that when the ratio of aeolian sand to loess is 1:0.4, the material has smaller deformation and stronger compressive capacity, which is used as the solid filling material in 2305 working face. In addition, when the 2305 working face is mined by caving method, the coal pillar has a large area of overall damage, the overall failure rate of the coal pillar is 93.7%. The overall failure rate of coal pillar is 88.6%, 14.9% and 11.4% when solid filling rate is 40%, 60% and 80%, respectively. Combined with the research results, the overall stability of coal pillar in overlying goaf can be effectively controlled when the filling rate is 60%.