海相软土盾构隧道围岩受力状态方程及其耦合求解方法OA

Marine soft soil,characterized by high compressibility,low strength,and structural fragility,is highly susceptible to large-scale plastic deformation and ground settlement under the disturbance of shield tunnel excava-tion,thereby posing a serious threat to engineering safety.Based on elastoplastic mechanics and limit equilibrium theory,a stress-state equation for surrounding rock applicable to marine soft soil is established and a semi-analyti-cal-numerical coupled solution framework featuring"logarithmic-spiral failure surface parameterization-integrated zonal governing equations-interface constraint conditions-Newton-Raphson iteration-finite element calibration"is proposed.Through theoretical derivation and algorithm implementation,the analytical-numerical unified solution for circumferential stress distribution and plastic zone radius is obtained,and is further validated based on a shield tunnel section of Shenzhen Metro Line.The results indicate that support pressure plays a decisive role in the stability of the surrounding ground.The radius of the plastic zone exhibits a nonlinear decay pattern with the increase of support pressure,showing the most sensitive"critical support pressure"characteristic within the range of 0.15～0.20 MPa;In the case study,when the support pressure exceeds 0.23 MPa,the plastic zone radius approaches the tunnel radius,and any further increase in support pressure yields only limited marginal benefit in controlling the surrounding rock deformation.Compared with purely analytical or numerical methods,the proposed semi-analytical-numerical coupled approach ensures not only physical transparency but maintains computational accuracy and engi-neering applicability.The findings can provide a theoretical basis and practical reference for the rational determina-tion of support pressure and construction safety control in shield tunnels constructed in marine soft soil.