The Stability Analysis Of Tunnel In Water-Rich Strata Based On Improved Zone State Index(ZSI)

As the demand for transportation increases,the regional distribution of tunnel projects in China has become more and more extensive,and the number has also increased.In the process of tunnel excavation,complex geology and groundwater conditions have seriously affected the stability of the tunnel surrounding rock,and at the same time,increased the difficulty of on-site construction and increased the engineering cost.However,at this stage,the evaluation indexes of surrounding rock stability are not perfect,and it is of great significance to conduct in-depth research on them.In this paper,the stability of the surrounding rock of the tunnel in the rich water area is studied from the following aspects:(1)On the basis of the existing yield and failure proximity,the zones’ stress and strain state is used to characterize the zone safety index,and the improved Zone State Index(ZSIsu)formula based on the subiquitous-joint is derived.The ZSIsu program is compiled through the FISH language and limited in FLAC3D.It was verified in the meta-software to evaluate the safety of the rock mass with more even joint distribution,and the influence of joint dip angle on ZSIsu was studied.(2)For jointed rock masses with different degrees of fragmentation,the parameter equivalent relations of Hoek-Brown criterion and Mohr-Coulomb criterion are derived,and the improved Zone State Index(ZSIhb)program based on Hoek-Brown criterion is derived and written.Run the program in the finite element software FLAC3D and MIDAS,compare and explain the correctness of the program,and analyze the influence of Hoek-Brown criterion strength parameter on ZSIhb.(3)Combining the ZSIsu program with the rock mass permeability coefficient,the formula for the units’ permeability coefficient varying with the unit yield failure degree is derived,which is implemented in FLAC3D through FISH language.The fluid-solid coupling simulation of a subway shield tunnel in Nanchang was carried out,and ZSIsu was applied to the safety evaluation of the palm face.The reasonable palm face support pressure was obtained.(4)Establish the relationship between ZSIhb and units permeability coefficient,and realize that the permeability coefficient changes with the unit state.The numerical simulation analysis of a local soft rock area of a highway tunnel in Jilin was conducted to study the spatial effect of surrounding rock during excavation.The stability and permeability coefficient of surrounding rock were analyzed through ZSIhb.Comparing and selecting the anchoring schemes of large deformation sections based on the displacement and the safety of surrounding rock.The optimization provides theoretical guidance for on-site construction.Through theoretical derivation and numerical analysis,the improved Zone State Index(ZSIsu)based on the ubiquitous-joint model and the improved Zone State Index(ZSIhb)based on the Hoek-Brown criterion are proposed to make up for the insufficiency of the surrounding rock safety evaluation.The comparison and selection of actual engineering support schemes provide references for similar projects,and the research content has theoretical significance and engineering value.