Study On The Evolution Of Mining Stress Based On Key Stratum Theory And Its Influence On Deformation Of Roadway

West return airflow dip located at butyl fourth mining area in No.8 Mine of Pingdingshan Coal Group,which performed large deformation characteristics under the influence of mining stress.The calculation results of abutment pressure based on traditional limit equilibrium theory showed that the roadway was out of the range of affected areas by mining,however,according to the site investigation and monitoring of abutment pressure,the roadway was within the range of significant influence of mining stress.Therefore,this thesis proposes a new solving thinking and method based on the theory of key stratum and elastic foundation beam in the background of geological conditions of butyl fourth mining area,the research is focused on the evolution law of mining stress based on key stratum theory and its influence on deformation of roadway which is within the range of mining influence,main study results and conclusions are summarized as follows:(1)According to the discrimination results of key stratum,a new solving method was proposed based on the theory of key stratum and elastic foundation beam,the abutment pressure formed in the hypogyny rock mass for each stratum group was calculated and stacked to the coal,then the evolution law of mining stress based on the theory of key stratum was obtained.The accuracy of calculation method was verified through mining stress monitoring of working face.(2)The physical similar model of mining stress evolution based on the similarity principle was established,which had the practical geological conditions of 14200 working face in No.8 Mine of Pingdingshan Coal Group as a background,through the analysis of similar simulation test results,the collapsing characteristic of overlying stratum in stope,evolution of mining stress in coal and the variation of vertical stress of roadway surrounding rock were obtained.It confirmed that the roadway was affected mainly by the mining stress.(3)According to the analysis of mechanics characteristic of roadway surrounding rock under the influence of mining stress,the mechanical model of roadway based on elastic-plastic theory was established,the rule of stress state,displacement distribution and plastic range of roadway surrounding rock were calculated under the influence of static pressure and mining stress according to the evolution law of mining stress;according to the establishment of numerical simulation model,the variation law of stress,displacement and plastic zone of roadway surrounding rock during the period of roadway driving and after the influence of mining stress were obtained.The study showed that the mining stress was main reason of roadway deformation.(4)According to the site investigation and detection of anchorage quality of anchor of west return airflow dip at butyl fourth mining area,deformation characteristics of roadway were obtained,the supporting scheme of full-face bolting-grouting combined support of roadway was proposed and implemented based on the analysis of deformation mechanism.The rationality of supporting scheme was verified through the monitoring of roadway surface displacement,and it achieved good technical and economic benefits finally.