Distribution Law of Mining Stress of the Gob-Side Entry Retaining in Deep Mining Thin Coal Seam

Tao Qin,Kai Ren,Lei Wang,Chen Jiang,Yanwei Duan,Zhi Liu,Zhijie Zhu

doi:10.1155/2021/5589948

Abstract

In order to explore the mining pressure development rule of gob-side entry retaining during deep thin coal seam mining, FLAC3D numerical simulation is applied to analyze the stress distribution rule of gob-side entry retaining, observing the left third working face of 49# coal seam in No. 8 mining area of Xinxing Coal Mine as the research object. The results show that the working face stress field is asymmetrical which is caused by the reserved roadway and the over goaf. After roadway tunneling, features of obvious stress redistribution are formed. The vertical and horizontal stress in the coal seam develop a U-shaped distribution. The vertical stress in the roadway is less than that in the lower roadway, and the horizontal stress is half that in the lower roadway. The phenomenon of high stress “nucleation” appears and becomes more obvious in the process of working face advancing, and the nuclear body disappears after working face advanced to the boundary line. With the working surface advancing, the trend of horizontal stress of gob-side entry retaining decreases gradually and the vertical stress of gob-side entry retaining is less than the original rock stress. The research findings provide a basis for the supporting design of gob-side entry retaining in the deep thin coal seam and the stability control of surrounding rock.

Highlights

With the continuous process of coal mining, shallow coal resources are almost depleted, and mining is gradually accessing deep mining areas
Thin coal seams of the mining areas account for 84.2%, and reserves are about 6 billion tons [2, 3]. e gob-side entry retaining can maximize the recovery of resources and reduce the amount of drivage. e problem of surrounding rock control in thin coal mining the gob-side entry retaining brings severe challenges to coal mine safety mining; especially, the problem of stable gobside entry retaining in Qitaihe thin coal mining area, which has already entered the process of deep mining, is becoming increasingly prominent
When excavation is carried out in the stratum, the surrounding rock stress is redistributed, continuously transferred to the interior, and the middle part of the working face presents the phenomenon of stress concentration. e vertical stress concentration occurs at the two sides of the surrounding rock, while the horizontal stress concentration occurs at the top and bottom of the surrounding rock. is paper aims at analyzing the stress distribution of the left three pieces of the gob-side entry retaining driving face and studying the stress distribution characteristics in the process of the gob-side entry retaining to driving face and driving face

Summary

Introduction

With the continuous process of coal mining, shallow coal resources are almost depleted, and mining is gradually accessing deep mining areas. The author combines the actual situation of working face in 49# Xinxing Coal Mine, using FLAC3D numerical simulation of thin coal seam gob-side entry retaining in the mining process to analyze the working face stress distribution characteristics. Given that the left three working faces use gob-side entry retaining to mine in Xinxing Coal Mine, the stress distribution, with stopped area of the left three working faces is affected by the left two mines the over goaf and the remaining roadway. By analyzing the stress distribution of the roadway driving model on the left three sections of the gob-side entry retaining (see Figures 5 and 6), it can be seen that the vertical stress concentration area of the coal seam is near the roof of the coal seam, and the horizontal stress concentration area of the coal seam is at the two sides of the upper and lower roadway. In spite of the quite small influence of thin coal seam tunneling on stress redistribution, the stress concentration zone is still formed in the middle of the coal seam. e residual roadway and the over goaf have a certain impact on the stress distribution, resulting in stress asymmetry

Analysis of Stress Distribution in the Over Goaf Roadway

Coal seam

Conclusion