复采工作面过空巷群顶板稳定性分析OA

Based on the urgent engineering needs of efficient recovery of coal mine resources and long-term safe and stable production of mines,the problems faced by the re-mining face under complex geological conditions have become more and more serious.In this paper,for the stability of the roof of the cross-gob roadway group of the re-mining face,FLAC3D simula-tion was used to reproduce the process of the re-mining face advancing through the over-gob roadway group,and the chan-ging law of the stress and plastic zone of the roof of the face was investigated,the influence of the pre-filling rate of the gob roadway on the maximum overhanging roof length of the roof of the face was analyzed,and the mechanical mechanism of the over-excessive fracture of the basic roof of the over-gob roadway group of the re-mining face was explored.The study shows that:When the distance of the re-mining face from the gob roadway group advances from 100 m to 0 m,the surrounding rock pressure will be transferred to the coal pillars on both sides of the gob roadway group and lead to the phenomenon of stress concentration,the stress concentration coefficient increases from 1.81 to 2.18,which affects the fracture step of the basic roof and the characteristics of the pressure,and the step of the pressure of the re-mining face is about 12～25 m.With the advancement of the working face,the working face roof plastic zone gradually extends to the pre-filling gob roadway group,resulting in a high rate of deformation of the surrounding rock.The plastic zone of the surrounding rock on both sides of the pre-filling gob roadway is distributed in the shape of"X",which leads to the reduction of elastic support area and the high speed growth of deformation of the surrounding rock.When the pre-filling rate of the gob roadway is 0%,86.4%and 100%,the step distance between the working face and the last collapse of the roof plate is 36 m,26 m and 15 m,respective-ly.When the width of the coal pillar of the gob roadway group is less than the critical value,it is easy to lead to the restora-tion of the roof of the mining face to be unstable and the length of the cantilever increases suddenly,and the fixed end's shear force and bending moment increase,leading to the advanced fracture of basic roof.