Research on layout and pressure relief control of roadway with residual coal pillar mining face

During the extraction of historical coal pillars and corner coal,there are some difficulties associated with the complex stress environment,severe surrounding rock condition,mining roadway significantly affected by the ground pressure,difficult layout and poor safety. Based on the background of the residual coal pillar mining face at the 52 mining area in Wangzhuang coal mine of Shanxi Lu'an group,the boundary of the residual mining face was divided into three categories as a regular gob boundary,a mixed gob boundary and an irregular gob boundary according to the distribution pattern of the mined area around the residual mining face. The stress distribution characteristics of the residual mining surface were revealed with the numerical simulation method as follows:①for the regular goaf boundary,the stress is symmetrically saddle-shaped; ②for the mixed gob boundary,the section coal pillar edge stress is unloaded,and the stress is transferred to the middle of the combined boundary of the mixed gob area leading to a high degree of stress concentration in the area and an increase in the scope of influence; ③for the irregular goaf area boundary,the coal is destroyed by the superposed stress in the corner area of the goaf area,and the concentrated stress is transferred to the deep corner area. The stress concentration factor with both sides of corner area perpendicular to the strike direction of the residual face is 2.2,and the two stress concentration factors with corner area parallel to the strike direction of the residual mining face are both 2.0. On the basis of the above observations,the layout principle of the roadway in the residual mining face was proposed that the roadway layout should avoid the stress superimposed zone at the boundary of the mining area and the tensile-shear failure area at the corner of the mining zone. The layout of the roadway in the mining face was determined with five typical coal pillar width,i.e., d₁=5 m, d₂=20 m, d₃=30 m, d₄=20 m,and d₅=5 m. Therefore,the roadway of the residual mining face was divided into three sections:original rock stress driving,gob side driving and high stress driving,the "3-5-3" zoning control system for the roadway in the residual mining face was established,the drilling pressure relief technology focused on the high-stress roadway was developed,the control parameters of the surrounding rock of the roadway was designed,and the industrial test was carried out. The monitoring data showed that the mining roadway can meet the requirements for the recovery of the residual mining face,which might provide a reference for the layout and control of the roadway in Lu'an and other mining areas.