考虑接头非线性转动效应的盾构隧道纵向变形简化解

    Simplified solutions for longitudinal deformation of shield tunnels considering nonlinear rotational effects of circumferential joints

    • 摘要: 纵向轴力和接头螺栓屈服会引起外荷载作用下盾构隧道环间接头转动刚度的显著非线性变化,现有盾构隧道纵向变形计算方法多是将隧道简化为具有恒定抗弯刚度的等效连续长梁,难以反映环间接头的非线性转动效应。首先,考虑盾构隧道横向性能和环间螺栓弹塑性行为,基于严格的隧道横断面椭圆参数方程推导其环缝分别处于弱拉弯、纯弯和压弯状态下的环间接头转动刚度计算公式;其次将盾构隧道沿纵向简化为一系列由非线性转动弹簧和线性剪切弹簧连接而成的Timoshenko短梁,同时采用沿隧道外壁均匀分布的法向和切向Winkler地基弹簧模拟土-隧道相互作用;然后借助状态空间法推导外荷载作用下盾构隧道纵向不连续位移解答,并提出轴向压力作用下隧道纵向变形迭代求解流程;最后通过对比已有理论方法和某基坑开挖引发下方盾构隧道纵向变形工程的实测结果验证所提方法的合理性,并基于某地表堆载诱发盾构隧道纵向变形的工程案例研究纵向轴力和横向刚度对隧道纵向变形的影响。研究结果表明:盾构隧道环间螺栓屈服会显著增大接头张开量和环缝的受拉面积;轴向压力的施加能够显著降低隧道因基坑卸荷引发的纵向位移、接头张开和环间错台变形。参数分析表明:随着纵向轴力由拉力增加为压力,既有隧道最大纵向位移和最大截面转角均逐渐减小,且减小速率先增大后减小,而最大接头张开量近似线性减小;既有隧道横向刚度的降低会导致其纵向位移和接头张开量的显著增加以及环间错台量的略微减小。

       

      Abstract: The longitudinal axial force and the yield of joint bolts can result in significant nonlinear variations in the rotational stiffness of circumferential joints of shield tunnels subjected to external loading. The existing computational methods related to longitudinal deformation of tunnels often simplify the tunnels as an equivalent continuous long beam with the constant bending stiffness, which are challenging to reflect the nonlinear rotational effects of circumferential joints. Firstly, taking the transverse performance and elastic-plastic behaviors of bolts of a shield tunnel into account, the expressions for the rotational stiffness of joints under weak tensile bending, pure bending and compressive bending conditions are derived based on the strict elliptic parametric equation for cross-section of tunnels, respectively. Secondly, the shield tunnel is modeled as a series of Timoshenko short beams connected by nonlinear rotational springs and linear shear springs along its longitudinal direction, meanwhile the soil-tunnel interaction is simulated using the normal and tangential Winkler foundation springs, which are evenly distributed on the outer wall of the tunnel. Then, the state space method is used to obtain the longitudinal discontinuous displacement of the shield tunnel under external loads, and the iterative solution process associated with its longitudinal deformation under axial pressure is proposed. Finally, the proposed method is validated by comparing the existing theoretical methods and measurements associated with the upper excavation-induced longitudinal deformation of the tunnel, and the parametric analyses are also carried out to explore the impacts of longitudinal axial force and transverse performance on surface surcharge-induced longitudinal deformation of the tunnel using an engineering case. The results show that the yield of longitudinal bolts can significantly increase the joint opening and tensile area between adjacent rings. The application of axial pressure can prominently reduce the longitudinal displacement, joint opening and shearing dislocation of the shield tunnel induced by the upper excavation. The parametric analyses show that as the longitudinal axial force increases from tension to compression, the maximum longitudinal displacement and rotational angle of the tunnel decrease nonlinearly, and the decrease rate at first increases and then decreases, while the maximum joint opening diminishes approximately linearly. The reduction of lateral stiffness of the tunnel can lead to significant growth in its longitudinal displacement and joint opening, as well as a slight diminution in the shearing dislocation.

       

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