Mechanical behavior of shield tunnel considering nonlinearity of flexural rigidity and leakage of joints

Partial leakage during operation of shield tunnel has great impact on the long-term safety of structures. It is difficult to simultaneously simulate partial leakage and mechanical properties of shield tunnel accurately. Hence, a combined simulation method is proposed. For partial leakage simulation, the homogeneous ring model is used and the corresponding seepage path is set at joint position. For mechanical calculation, a shell-spring-contact-ground model considering the nonlinearity of flexural rigidity of segment joints is established to replace the homogeneous ring model. The real stress state of lining is obtained by iterative calculation. The distribution of pore water pressure around tunnel and the mechanical behavior of structures are analyzed under different seepage flows and leakage locations. The results show that the pore water pressure decreases more significantly and the internal force of structures changes more obviously with the increasing seepage. The leaking joint close to tunnel hance has more obvious effect on its internal force. The affected areas of joint leakage exhibit consistency. Taking the leaking joint as the center, the 36-degree areas at its both sides are severely affected, the 48-degree and 60-degree areas are generally affected, and the remaining areas are weakly affected. For the composite strata, compared with these under hydrostatic pressure conditions, the upper and lower leakages lead to the increase of upper and lower positive bending areas, and the distribution of axial force along the whole ring is uneven. The average axial force at the leakage side is less than that at the non-leakage side, which is unfavorable to the safety of segment structures.