Test research on advance abutment pressure caused by coal mining based on optical fiber monitoring

Abstract

The strata movement and deformation caused by underground mining activities is a typical “black box” problem, it is difficult to grasp the structural characteristics of complete overburden and the law of ground pressure. Abutment pressure is the vertical supporting force acting on coal and rock mass due to the redistribution of surrounding rock stress caused by underground engineering excavation. The distributed optical fiber and fiber Bragg grating are implanted into the physical similar model to monitor the distribution characteristics of abutment pressure in front of the working face during the whole excavation process. The results show that FBG monitoring to reach the peak strain needs to meet two conditions: the working face passes under it, and the cantilever beam structure above the working face is unstable and collapses, and the grating is located at the end of the suspended fixed beam. When FBG is located in front of the working face, the whole process is divided into four stages: 150-81 m from the grating is the weak influence area; 81-49.5 m is the significant influence area; 49.5-21 m from the grating is the severe influence area; 21-0 m from the grating is the influence recovery area. Based on this, the abutment pressure distribution model of FBG sensing detection is given. The influence range is within 81 m, the peak value is 21 m in front of the working face, and the pressure relief area is directly above the working face. The distributed optical fiber monitoring results show that the upward compressive stress value of the abutment pressure affected area decreases rapidly, and enters into the high roof tensile stress affected area. The tensile stress distribution presents a single peak shape, and gradually decreases after reaching the peak until it returns to the elastic area. The research results provide a new research idea for abutment pressure monitoring caused by mining.