Coal Pillar Width Effect And Segmented Support Technology For Surrounding Rock Stability Of Facing Mining Roadway

As an unconventional means,facing roadway can effectively alleviate this problem under the condition that mining replacement is very tight.There are five stages in the whole operation period of open roadway: solid coal excavation stage,head-on stage,head-on stage,goaf excavation stage and secondary mining stage.The surrounding rock deformation of roadway affected by multiple mining is different from that of ordinary mining roadway,and its stability is affected by geological conditions such as coal body strength,roof lithology,coal pillar width,support technology and other production conditions.Based on the engineering background of9103 Transportation Chute in Hehe Coal Mine,this thesis adopts the research methods combining laboratory experiment,theoretical analysis,numerical simulation and field test to carry out research on the coal pillar width effect and subsection support technology of the facing mining roadway,and successfully alleviates the tension of mining replacement in Hehe Coal Mine.The main achievements are as follows:(1)Mechanical properties of coal under multiple loading and unloading: Based on multiple loading and unloading experiments,the stress-strain curve of coal body is obtained,the hysteretic effect of coal body is analyzed,the deformation law and energy evolution law of coal body under multiple loading and unloading are obtained,and the failure energy criterion of coal body is summarized.Applying the plane strain principle and defining the damage variables,a coal damage constitutive model is established.The model fits well with the experimental curve,and can accurately reflect the stress-strain relationship of coal with similar properties under multiple loading and unloading,which provides a basis for the subsequent theoretical analysis and numerical simulation.(2)Study on the effect of coal pillar width on the stability of surrounding rock of mining roadway: Through theoretical analysis and numerical simulation,the "F" type overburden cantilever structure formed by the coal pillar and the roof above it and its mechanical action are analyzed.According to the distribution of supporting stress and the deformation zoning characteristics of coal pillar,coal pillar can be divided into cracked coal pillar,plastic coal pillar,elastic coal pillar with rising stress and elastic coal pillar with gentle stress.By analyzing the influence of coal pillar type on the stress field,displacement field,plastic zone and energy evolution law of roadway surrounding rock and combining with the engineering conditions of coal mine,a reasonable elastic coal pillar with a stress rise of 20 m is determined.(3)Study on sectional-level support technology for surrounding rock stability of mining roadway: The temporal and spatial evolution characteristics of stress field in facing roadway under different types of coal pillars are compared,and the evolution law of stress field in surrounding rock of facing roadway is summarized.The influence range of mining is obtained from 30 m in front of working face to 60 m behind working face,and the timing of stopping and resuming excavation in 9103 transport channel is determined as: 60 m away from 9102 working face to stop excavation,150 m away from 9102 working face to resume excavation.By simulating the supporting efficiency of bolt under different types of coal pillar,the restrictive effect of bolt support under plastic coal pillar,the limiting effect under elastic coal pillar with rising stress,and the protective effect under elastic coal pillar with gentle stress are obtained.Based on the engineering conditions of good-coal mine,the parameters of bolt support are determined,and the technical scheme of surrounding rock stability control of mining roadway with "reasonable coal pillar width +subsection support" is proposed.(4)Industrial test: in-situ monitoring of roadway surrounding rock deformation and mining stress was carried out.The results show that the proposed subsection support technology can effectively control surrounding rock deformation(the maximum deformation of roof and floor is about 162 mm,and the maximum deformation of side is about 196mm),and good practical results have been achieved.There are 114 Figures,18 Tables and 81 references in this thesis.