| In recent years,the construction of traffic facilities in China is in full swing,longdistance and deep-buried tunnel projects are also common,and many deep-buried tunnels are in water-rich strata.After tunnel excavation in water-rich strata,the stress redistribution of surrounding rock leads to changes in porosity,number of cracks and crack opening of surrounding rock,and then the seepage field is formed around the tunnel.The seepage force will affect the stress and deformation of surrounding rock,and the stress and deformation will act on the seepage field,which is hydraulic coupling.The hydraulic coupling effect often weakens the surrounding rock and reduces the stability of the tunnel.Therefore,it is particularly important to study the hydraulic coupling effect of deep-buried tunnels.In this paper,the evolution law of permeability and effective stress coefficient is studied,and then the hydraulic coupling analysis of elastic-brittle plastic rock mass and strain-softening rock mass is carried out respectively.Finally,combined with the engineering example of Yuximolegai tunnel,the stress and deformation of tunnel surrounding rock are studied,and the influence of different parameters on the tunnel is analyzed,which provides help for the construction of deep-buried tunnels.The following results have been achieved :(1)Based on the triaxial compression seepage test data of granite and sandstone,the permeability and Biot coefficient evolution functions with confining pressure and plastic strain as variables are fitted respectively.It is found that the permeability and Biot coefficient have similar evolution law,both decrease with the increase of confining pressure and increase with the increase of plastic strain,and remain stable after reaching the critical plastic strain.(2)On the basis of considering the different permeability coefficients and Biot coefficients of plastic zone and elastic zone,the closed-form solution of water-rich circular tunnel in elastic-brittle-plastic rock mass is derived.The analysis of the influence of different parameters shows that the stress distribution and the surrounding rock characteristic curve are basically the same under different permeability coefficients and Biot coefficients.With the increase of Biot coefficient,the plastic radius and displacement increase significantly,while the water inflow changes little.With the increase of permeability coefficient,the pore water pressure in plastic zone decreases significantly,and the water inflow is on the contrary.(3)On the basis of considering the change of surrounding rock parameters with gradual failure,the closed-form solutions of water-rich circular tunnel in strainsoftening rock mass are derived by using MC and HB yield criteria respectively.The results show that with the decrease of support force,the radius of residual zone,the radius of plastic zone,displacement and water inflow increase significantly,and the growth rate increases,while the initial pore water pressure and the volume modulus of rock skeleton are opposite.The increase of permeability coefficient will lead to the overall decrease of pore water pressure distribution,and the change of mechanical parameters is mainly concentrated in the softening zone.(4)Different sections of Yuximolegai tunnel are selected as elastic-brittle-plastic and strain-softening rock masses for research,and the surrounding rock states of different sections are analyzed.It is found that the stress distribution laws of the two surrounding rocks are basically the same.Further study shows that with the increase of pore water pressure,the radius and displacement of plastic zone show an approximate linear growth trend.Water inflow has a similar effect on the surrounding rock of tunnel,while the effect of supporting force is opposite.The influence of supporting force is mainly in the plastic radius and displacement,and has little effect on water inflow.There are 53 pictures,15 tables and 98 references in this thesis. |
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