Failure Rules And Stability Control Of The Plastic Zone In The Repeated Mining Roadway

Coal plays an important role in China’s energy consumption,with the increase of domestic demand for coal energy consumption,coal mining intensity is also increasing,in order to meet the coal mining continuation,at the same time to reduce the number of working face move,more and more coal mines adopt the dual lane layout.The characteristics of the layout of double roadway lie in that after the stoping of this working face,the stoping roadway is retained and served for the next working face,while the retaining roadway is served for two working faces,and the maintenance time is very long.Under the influence of repeated mining,the roadway is faced with severe ore pressure,and the retaining roadway is faced with difficulties in support and maintenance.In view of the above problems,this paper takes the return air roadway of 22205 working face of Shendong Bourtai Mine as the research background.Based on the field investigation and theoretical analysis,a numerical simulation model is established to determine every 100 m of advance of the working face,and a stage analysis is carried out on the stress cloud map and the maximum stress of the return air roadway of 22205 working face.The three measuring points 100 m,500m and 900 m apart from the open-cut hole were used to analyze the stage changes of the maximum principal stress,minimum principal stress and differential stress at the measuring point,the stage changes of the plastic zone of the measuring point and the stage changes of the surrounding rock displacement at the measuring point.By analyzing the stage changes of roadway stress,plastic zone and surrounding rock displacement,the following conclusions are drawn.With the expansion of the working surface,the range of the stress nebulogram is also expanded.Compared with the change of the maximum value and difference value of the stress nebulogram,the change of the secondary mining is greater.In the process of primary and secondary mining,the variation of roadway can be divided into the stages of underfull mining,first moving expansion,stability after primary mining and expansion of secondary mining.Principal stress and principal stress difference at measuring point with the four stages of the whole roadway phase change trend,the stress changes little tunneling effect and stable stage,a bigger than the first stage of stress mining expansion phase,a stable stage after mining stress is increased after stabilization,the secondary mining phase extension stress values increase sharply.The variation range of plastic zone at the three measuring points is consistent with the trend of stress variation.Tunneling effect stage stage plastic zone range is almost not changed,a mining expansion phase obvious expanding range of plastic zone,a mining after the stable phase of the plastic zone expanded in a mining stage expanding scope remain stable for a range of plastic zone,on the basis of the secondary mining rapid increasing range extension stage plastic zone.The upper roof is larger than the two sides,the two sides are larger than the floor,the coal wall is larger than the coal pillar,and the floor is the smallest.The variation trend of surrounding rock displacement in the measuring point stage is the same as that in the stress and plastic zone stage.Displacement of surrounding rock in four stages on changes,displacement of surrounding rock drivage influences the stage of stable order does not change,a mining expansion phase change rapidly and displacement of surrounding rock after a mining stable phase displacement of surrounding rock in a mining expansion phase displacement displacement unchanged,on the basis of the secondary mining expansion phase displacement of surrounding rock dramatic change.The displacement change of the upper roof is greater than that of the coal wall and the coal pillar.In comparison,the change of the coal wall is greater than that of the coal pillar,and the change of the floor displacement is very small.Based on the study of the stage failure of the plastic zone of the repeated mining roadway,the scheme basis for the support of the repeated mining roadway by stages was provided,and good support effect was obtained in the field application.