Shield tunnels with great longitudinal differential deformations will adversely affect the service performance and optional safety of the metro system. Previous studies on the longitudinal mechanical behavior of shield tunnel are mostly carried out within the framework of elastic or elastic–plastic theory. However, assuming the concrete as elastoplastic body cannot properly reflect its nonlinear mechanical characteristics such as strain softening, stiffness degradation, etc., while damage or crack inevitably occurs when shield tunnel suffers large deformations. Therefore, the nonlinear damage characteristics of concrete material are considered in this paper, a novel positive/negative decomposition of stress tensor in energy norm is introduced herein to consider the asymmetric tensile/compressive material behavior of concrete, and a bi–scalar damage constitutive model of concrete is developed in turn. Then, to investigate the damage and degradation mechanisms of shield tunnel with differential deformation, the 3D discontinuous contact model is employed to develop the elaborate tunnel–soil numerical model. Results show that when shield tunnel suffers differential deformation, tensile damage dominates while compressive damage is minor, additional shear force and bending moment are induced, the ovality of tunnel cross section and serviceability also vary along the longitudinal direction. The damage and degradation of concrete material will reduce the tunnel integral stiffness and attenuate its ability to resist longitudinal and circumferential deformation. Besides, the segmental rebar is hard to yield, while the longitudinal coupling bolts on the lower half of tunnel segments with large deformation are inclined to yield. It should be noted that, the segmental rings near the inflection point of longitudinal deformation profile are most severely damaged, and exhibit the largest convergence deformation and lowest serviceability, where special attentions should be paid.

具有较大纵向差异变形的盾构隧道将不利地影响地铁系统的服务性能和可选的安全性。以前对盾构隧道纵向力学行为的研究大多是在弹性或弹塑性理论的框架内进行的。但是，假设混凝土为弹塑性体，则不能正确反映其非线性机械特性，如应变软化，刚度降低等，而当盾构隧道大变形时不可避免地会发生破坏或开裂。因此，本文考虑了混凝土材料的非线性损伤特性，在能量范数中引入了一种新的正/负应力张量分解，以考虑混凝土的不对称拉伸/压缩材料性能，进而建立了混凝土的双标量损伤本构模型。然后，为研究具有不同变形的盾构隧道的破坏和退化机理，采用3D不连续接触模型建立了精细的隧道-土体数值模型。结果表明，当盾构隧道发生差异变形时，拉伸损伤占主导地位，压缩损伤较小，诱发了额外的剪切力和弯矩，隧道截面的椭圆度和使用寿命沿纵向也发生变化。混凝土材料的损坏和降解将降低隧道的整体刚度，并削弱其抵抗纵向和周向变形的能力。此外，分段钢筋很难屈服，变形较大的隧道段下半部的纵向连接螺栓倾向于屈服。应该注意的是，在纵向变形轮廓拐点附近的扇形环受到最严重的破坏，并且呈现最大的会聚变形和最低的可使用性，应特别注意。