Detection and Theoretical Numerical Simulation of the Failure Depth of the Bottom Plate in Belt Pressure Mining

Abstract

Aiming at the problems of safety production cost caused by the increase of mining face width and pressure mining in Xizhuo Coal Mine in Chenghe Mining area, a mechanical model of floor plastic slip failure is established based on the theory of plastic slip line, and the difference between it and the traditional floor failure model is analyzed. The damaged contour line of the support stress and lateral support stress on the bottom plate through the advancing direction of the working face is the intersection line of a straight line and an arc line. The failure of the floor caused by lateral supporting stress is the failure of the floor again on the basis of the failure of the floor in the advancing direction of the working face, and there is a superimposed failure area. The analysis of the failure form of the stope floor by this mechanical model is closer to the engineering practice. By using “ultrasonic detection method + stress monitoring inverse analysis method,” the measured data such as disturbance failure depth and distribution law of large mining width working face were obtained. The test method used in this paper is relatively rare in the monitoring of the depth of floor disturbance failure at home and abroad. Considering that the traditional pressure water test method has disadvantages such as easy collapse hole, long period, and large error in monitoring the failure rule of deep floor rock mass, the embedded stress monitoring and reverse analysis method and ultrasonic detection method are used to successfully collect and real-time monitor the data of rock floor before, during and after mining in the lower part of wide mining face of Xizhuo Coal Mine for the first time, and several effective data are obtained, which solves the three-part “spatial-time” all-round floor disturbance and failure law field measurement which cannot be realized by traditional testing technology. By comparing the results of theoretical analysis, field measurement, and numerical simulation, the law and depth of floor disturbance failure of a 240-m wide mining face in the Chenghe mining area are obtained for the first time, which provides scientific guidance for floor water disaster induced by coal seam mining under similar conditions in the future and has an important reference role for the prevention and control of Ordovician ash water disaster in coal mining. It provides important technical parameters for the safe setting of the effective water barrier layer and the selection and timing of the grouting layer of the floor, which can bring considerable economic and social benefits. The research results have important popularization value.