Study On Stability Control Technology Of Biased Tunnel And Slope In Weak Stratum

Tunnel engineering makes transportation more convenient and provides guarantee for economic development.However,the topography and geology of tunnel portal section are often complex,and tunnel construction often encounters various engineering geological problems.Based on the Yangmei tunnel entrance section project,combined with theoretical knowledge,this thesis studies the deformation mechanism and related control technology of biased tunnel and slope in weak stratum.The finite element method is used to study the influence of different excavation methods and initial support parameters of biased tunnel in weak stratum on the stress and strain of tunnel entrance section.The field measurement is carried out,and the measured data are compared with the simulated data.The main work is as follows:(1)By analyzing the engineering geological conditions of Yangmei tunnel entrance section,the main factors affecting the deformation of Yangmei tunnel entrance section are: topography,lithology and engineering properties.The deformation mechanism of tunnel surrounding rock and slope deformation is studied,the deformation control measures of tunnel entrance section are summarized,and the control measures of advanced small pipe grouting and surface grouting are analyzed in detail.(2)The numerical simulation of Yangmei tunnel is carried out by MIDAS / GTS NX software.The stress and strain of the tunnel under different construction methods are compared and analyzed.The results show that the vault and slope settlement are large when the tunnel is excavated.Among the different excavation methods,the influence of the core soil method on tunnel surrounding rock and slope is relatively small.Considering economy and construction,the thickness of shotcrete for primary support is optimized around 26 cm.And based on the strength reduction method,the influence of advance small pipe grouting reinforcement and surface grouting on the entrance section of tunnel is studied.The results show that the settlement of tunnel vault is significantly reduced,and the stability of tunnel is significantly improved.(3)According to the deformation monitoring,data processing and analysis of surrounding rock and slope of biased tunnel,the deformation law of surrounding rock and slope of biased tunnel is summarized.According to the analysis of typical sections,the deformation rate is fast and the deformation is large in the early stage of tunnel surrounding rock and slope deformation.In the late stage of deformation,the deformation rate gradually decreases.The maximum ground settlement of the left tunnel section is 43.9 mm,and the maximum crown settlement is 28.6mm;the maximum ground settlement of the right tunnel section is 19.7mm,and the maximum crown settlement is 15.2 mm.The measured data are compared with the simulation results,and the reasons for the differences are analyzed.