Mechanical mechanism and load-bearing performance regulation of upward re-mining floor coal pillar filling to increase stability
摘要
The instability of the bottom coal pillar induces the collapse of the coal pillar at the upward re-mining working face threatens mine safety, and ensuring the mining stability of the bottom coal pillar is the key to the safe recovery of left-over coal seam. In order to solve the problem of upward re-mining in No.6107 working face of Yuanbaowan coal mine, the law of stress distribution in the bottom coal pillars under the lateral clamping effect of the filling body is explored and the law of deflection of the shear stress trajectory under the lateral limit effect and its strengthening mechanism on the bearing capacity of the bottom coal pillars is revealed through theoretical analysis, FLAC3D numerical simulation, and engineering practice. The correlation characteristics of the “vertical stress drop and dissipation energy concentration zone connection” of the mined coal pillar are found, and the dual indicator type of “vertical stress reduction + dissipation energy concentration zone connectivity” is proposed to determine the instability of the mined coal pillars and the enhancement effect of the filling body strength on the bearing capacity of the bottom coal pillars is revealed. The results show that: The shear stress trajectory in the bottom coal pillar is deflected under the action of filling body clamping, and when the filling body clamping force increases from 1.0 MPa to 5.0 MPa, the same shear stress trajectory transitions from monoclinic penetration type to V-shaped, and the shear stress components on both sides of V-shaped form slip-inducing and slip-resisting sections and both cancel each other and the critical monoclinic shear damage stress increases with the increase of filling body strength. The critical monoclinic shear failure stress increases with the increase of filling strength. No.6 and No.7 coal pillars are destabilized, and the maximum dissipation energy in the two pillars develops from the upper left and lower right corners toward the center of