Study On Stability And Supporting Timing Of Highway Tunnel Based On Deformation And Stress Of Surrounding Rock

In order to optimize the support timing during the construction of highway tunnels,based on the Tian’e-Beihai Ganglingpo highway tunnel project,supported by the on-site monitoring data during the tunnel construction process,with the minimum construction safety clearance of the tunnel face and the deformation of the surrounding rock as the indicators,and based on The maximum support force of the retaining structure,aiming at the stress state of the tunnel face and the interaction between the deformation of the surrounding rock and the support force,the simplified force model of the beam plate and the displacement-convergence analysis method are used respectively.A method for determining the support timing of the tunnel face and the surrounding rock during the construction of highway tunnels is proposed.The research results can provide method support for the optimal design and safe construction of surrounding rock supporting structure of highway tunnel.The main research contents and conclusions are as follows :(1)Based on the comprehensive analysis of the engineering geological conditions of Ganglingpo highway tunnel in Tian-Ba highway(From Fengshan to Bama in Tian’e county),four monitoring sections with typical geological characteristics were selected,including K0 + 356 surface section at the right tunnel entrance,ZK2 + 168 surface section at the left tunnel exit,K0 + 353 vault section at the right tunnel entrance and ZK2 + 160 vault section at the left tunnel exit.The deformation and of monitoring data in the construction process of tunnel surrounding rock were analyzed by using the polynomial function and ’ S ’ function in the statistical regression analysis model.On this basis,the displacement change rate was taken as the index,combined with the construction process.The deformation of surrounding rock is divided into three stages : rapid growth stage,gentle increase stage and stable stage data support for predicting the displacement trend and value of tunnel surrounding rock and optimizing the timing of primary support.(2)On the basis of analyzing the distribution characteristics of unfavorable geological structure of surrounding rock and its spatial relationship with tunnel face,the interaction between structure and tunnel face rock plate is generalized into three kinds of stress analysis models,which are fixed beam model,simply supported-fixed beam model and simply supported beam model.Then,taking the analysis of the tensile-bending and shear failure modes of tunnel face rock plate as the criterion,the method of determining the minimum safety clearance of tunnel face stability is proposed.On this basis,the ZK019 + 920 section of Gang lingpo Tunnel of Tian-Ba Expressway is selected.Based on the mechanical parameters of surrounding rock obtained by experimental research,combined with the equivalent circle approximation method of non-circular caverns,the influence of unfavorable geological structure height H,width a,inclination angle θ and construction technology on the minimum safety clearance of the rock plate of the tunnel face is studied.Through the comparative analysis with the analysis results of other mechanical models,the rationality and accuracy of the method for determining the minimum safety clearance of the tunnel face proposed in this paper are further demonstrated,which provides method support for the determination and optimization of the advance support time in the construction process of the tunnel face.(3)Based on the convergence-constraint analysis method of tunnel surrounding rock displacement and support,combined with the equivalent circle approximation method of non-circular cavern,the analysis of surrounding rock support timing is transformed into the study of the relationship between surrounding rock displacement,support force and construction process.The elastic-plastic theory of circular tunnel is adopted to analyze and establish the curve of surrounding rock deformation and support force,longitudinal deformation and support process,so as to determine the corresponding surrounding rock deformation and support force in the support process/On this basis,combined with the combined force analysis method of tunnel support measures,a method for determining the support timing of tunnel surrounding rock based on convergence-constraint is given.Furthermore,the supporting time of surrounding rock in K0 + 353 section at the entrance of Ganglingpo tunnel of Tian-Ba highway is analyzed.It is considered that the optimal supporting time is when the radial displacement is 3.15 mm under the unfavorable geological structure and the designed supporting structure.At this time,the supporting force is about 661 k Pa,and the final deformation of surrounding rock is about 5.13 mm.Figure [59] Table [20] Reference [101]...