Study On The Stability Of Surrounding Rock Of Deep Buried Tunnel Considering Layered Characteristic

With the rapid development of our economic modernization construction,the metal mining industry in shallow layer resources can not meet the needs of development,slowly toward deep mining.With the increasing mining depth,the complex engineering geological conditions of deep rock mass,coupled with the influence of high ground stress and other factors,make the research on the stability of deep roadway surrounding rock extremely complicated.For deep buried layered rock mass,the influence of rock structure on the stability of roadway surrounding rock cannot be ignored.Based on the engineering background of Mengnuo mining area in Yunnan province,this paper studies the composition,water absorption properties,rock strength and loose circle size of roadway surrounding rock by geological survey,field test,indoor and outdoor test,theoretical analysis,numerical simulation and other research methods,and analyzes the physical characteristics of layered surrounding rock in the mining area.On this basis,the factors affecting the stability of roadway surrounding rock are analyzed through analytic hierarchy process,and the factors affecting the stability of surrounding rock are studied.Finally,the stability of roadway surrounding rock is analyzed based on the engineering practice and numerical model is established.The main research contents and achievements are as follows:(1)Field investigation and data collation were carried out on the engineering general situation of the mining area and geological characteristics such as stratum lithology,geological structure and hydrogeological conditions.The emphasis was placed on the statistical analysis of the ground stress,structural plane spacing and dip Angle of the mining area.The geological stress field of the mining area was dominated by horizontal stress,and the distribution characteristics of structural plane spacing and dip Angle were obtained.(2)Through X-ray diffraction(XRD)test,the mineral composition and content of the main rock samples of the roadway were compared and analyzed,among which there were different clay mineral compositions,which weakened the strength of the roadway surrounding rock and made it more sensitive to water.In addition,the water texture experiment of the rock samples was carried out to analyze the water texture characteristics of the surrounding rock,and the water absorption rate of the surrounding rock samples was measured between 0.38% and 0.98%.The field test of surrounding rock loose circle is carried out,and the distribution range of surrounding rock loose circle is 2.07m～5.75 m,which belongs to the unstable surrounding rock with large loose circle.(3)Through analytic hierarchy process,the influencing factors of surrounding rock stability were analyzed,and the weight of each factor was obtained.It was concluded that the influencing degree of surrounding rock stability was ranked as rock strength,rock dip Angle,tunnel depth,groundwater and rock thickness.(4)The discrete element numerical simulation software 3DEC was used to calculate and analyze the deformation of roadway surrounding rock of deep stratified rock mass under the conditions of different burial depth,different rock thickness and different rock dip Angle.The deformation and failure characteristics of roadway surrounding rock under different bedding conditions,the key locations of the main deformation of roadway,the stress change process of roadway surrounding rock and the distribution range of the plastic zone of roadway surrounding rock are studied,which provides a theoretical basis for the subsequent support of roadway surrounding rock.