Stress Evolution Law And Surrounding Rock Control Of Fractured Mudstone Roadway Under Mining And Tunneling

The surrounding rock of cataclastic mudstone roadway has the characteristics of low strength,easy weathering and disintegration,and poor long-term stability.Under the influence of underground mining disturbance in coal mine,it is easy to cause the expansion of fracture circle of roadway surrounding rock,large deformation of surrounding rock,and long-term stability control problem,which seriously restricts the safety of roadway construction during mine infrastructure construction and operation.This thesis takes the central auxiliary transportation roadway of Libi Coal Mine in Qinshui County,Jincheng City,Shanxi Province as the research background,and comprehensively uses a variety of research methods to systematically study the engineering geological characteristics of the surrounding rock of the cataclastic mudstone roadway,the mechanical properties of the fractured mudstone,the surrounding rock stress environment,and the surrounding rock control.Based on the comprehensive test and evaluation of the engineering geological conditions of the central auxiliary roadway,the mechanical weakening law and failure characteristics of the fractured mudstone are analyzed,the main influencing factors of the deformation and failure of the fractured mudstone roadway are clarified,and the stress evolution law of the roadway surrounding rock under the influence of mining disturbance is revealed.The surrounding rock control technology of the fractured mudstone roadway is proposed and the support design parameters are simulated and optimized.In order to further verify the feasibility of the surrounding rock control technology,the field support application is carried out in the test roadway section and the monitoring station is arranged to monitor the mine pressure.The main research results are as follows:(1)Summarize the engineering geological characteristics of the surrounding rock of the central auxiliary transportation roadway.The lithology of the surrounding rock of the roadway is poor and the crushing is more serious.In the later stage,it will be affected by the disturbance of the adjacent roadway excavation and the mining of the working face,and the long-term stability is difficult to guarantee.The laboratory test and analysis of the physical and mechanical properties,components and microstructure of the mudstone in the central auxiliary transportation roadway show that the strength of the roof mudstone is high,which can not directly reflect the mechanical properties of the broken mudstone in the shallow part of the surrounding rock.The mudstone has high clay content,developed joints and fissures,and poor cementation of mineral particles.The basic quality classification of the surrounding rock of the roadway is carried out.The surrounding rock of the central auxiliary transportation roadway is grade V surrounding rock.(2)The failure law of fractured mudstone is analyzed theoretically.The deformation characteristics of fractured mudstone are mainly characterized by decreased strength and increased deformation.A numerical calculation model was established to study the mechanical properties and failure characteristics of mudstone under different fracture densities,different fracture positions,different loading speeds and different fracture dip angles.With the increase of fracture density,the compressive strength and elastic modulus of rock decrease obviously.The closer the crack position is to the loading side,the lower the strength is,and the crack propagation develops to the loading surface.The loading speed also has a certain influence on the bearing capacity of mudstone.The larger the loading speed,the stronger the bearing capacity of fractured mudstone.The larger the crack dip angle,the stronger the uniaxial compressive strength,and the more obvious the post-peak brittleness characteristics.(3)The influencing factors of surrounding rock failure in the central auxiliary transportation roadway are analyzed.The main influencing factors are: high ground stress,poor lithology,poor stress environment,large roadway section,insufficient bolt depth and so on.The main influencing factors such as buried depth,pressure coefficient and surrounding rock strength are analyzed by numerical simulation.The results show that the buried depth and pressure coefficient determine the stress environment of roadway surrounding rock to a certain extent.The larger the buried depth and pressure coefficient are,the higher the surrounding rock stress is.The deformation of roadway and the expansion of plastic zone increase gradually.The strength diameter of surrounding rock determines the control difficulty of roadway surrounding rock.The lower the strength of surrounding rock is,the larger the range of plastic zone of surrounding rock and the deformation of roadway are.The control difficulty of grade IV and grade V surrounding rock increases greatly.(4)The influence of excavation disturbance and mining disturbance on the stress environment of roadway surrounding rock is studied.The stress evolution law of surrounding rock during roadway excavation is analyzed.With the roadway excavation,the stress of surrounding rock is in a certain dynamic balance.According to the stress distribution characteristics of the roadway axis direction,the stress axis direction can be divided into three disturbance areas.The stress disturbance during the excavation of the adjacent rock roadway is analyzed theoretically and simulated.The minimum rock pillar width without disturbance is calculated theoretically and verified by numerical simulation.The stress disturbance during the excavation of the adjacent coal seam roadway is simulated and analyzed,and the characteristics and size of the stress disturbance are obtained.According to the stress evolution law of surrounding rock,the plastic zone of surrounding rock and the deformation characteristics of roadway surrounding rock during mining,the deformation and plastic zone expansion of roadway surrounding rock are basically corresponding to the stress environment of roadway surrounding rock.In order to ensure the long-term stability of surrounding rock of mudstone roadway group,the reasonable width of main roadway protection coal pillar is 120 m.(5)The surrounding rock control scheme of the fractured mudstone roadway in Libi Coal Mine is proposed.According to the engineering geological conditions of the surrounding rock of the roadway,the deformation and failure characteristics of the surrounding rock and the mining disturbance in the later stage,an optimized support scheme for the surrounding rock control technology of the fractured mudstone roadway is proposed.In order to further verify the feasibility of the surrounding rock control scheme,the field support application is carried out in the test roadway section and the monitoring station is arranged to monitor the mine pressure.The monitoring results show that the surrounding rock control effect is good,and the surrounding rock deformation and fracture circle expansion are effectively controlled.There are 81 figures,13 tables and 111 references in this thesis.