Stability And Control Of Surrounding Rock For Construction Of Deep Buried Tunnel In Basalt Strata With High In-situ Stress

With the gradual improvement of national infrastructure,the number of underground projects under high in-situ stress will be increasing.Tunnel construction of hard rock and soft rock under high in-situ stress will face the engineering and technical problems of rock burst and large deformation respectively.Therefore,the study of hard rock burst and soft rock pressure under high in-situ stress has important reference value for the stability and control of tunnel surrounding rock.Based on shizishan tunnel of central Yunnan Water Diversion Project,this paper analyzes the surrounding rock stability and control technology of hard and soft basalt strata tunnel under high in-situ stress by means of laboratory test,theoretical analysis,numerical simulation and field monitoring,the conclusion can provide reference for the stability and control technology analysis of rock mass with high in-situ stress in shizishan tunnel and similar projects.The main research work and conclusions are as follows:(1)The mechanical strength of hard and soft basalt and the physical and mechanical parameters of basalt based on H-B criterion and M-C criterion were obtained by indoor mechanical tests.It provides data basis for the follow-up study of surrounding rock stability in hard and soft basalt strata construction.(2)Based on the energy criterion,the rock burst grade of hard basalt strata and its sensitivity to initial stress,disturbance coefficient and lateral pressure coefficient are obtained.The stability of hard surrounding rock is analyzed based on catastrophe theory and interval theory.Finally,combined with the energy release of hard strata and the maximum depth of potential instability of surrounding rock,the support structure of hard basalt strata with high in-situ stress is quantitatively studied.(3)The distribution characteristics of soft basalt pressure arch under different lateral pressure coefficients and initial stress are analyzed,and the calculation method of surrounding rock pressure based on pressure arch effect is proposed.The applicability of platts theory,field measurement,hydraulic tunnel design method and surrounding rock pressure calculation method based on pressure arch effect in high in-situ stress stratum are compared and analyzed.The safety of supporting structure under different calculation methods of surrounding rock pressure is obtained.(4)Taking pressure arch,surrounding rock pressure,limit energy storage and surrounding rock stress change characteristics as indexes,the stability differences between hard basalt and soft basalt strata are analyzed.(5)Combined with the site construction and surrounding rock properties of shizishan tunnel,the control technology of tunnel construction under hard and soft basalt stratum with high in-situ stress is put forward.