加卸载对盾构隧道材料损伤和结构特性的影响
Effects of Material Damage and Structural Characteristics on Tunnel Shield During Loading and Unloading

为研究加卸载对盾构隧道结构受力和材料损伤状态的影响，基于混凝土塑性损伤本构、非线性接触理论和Python二次开发，用全周单向受压弹簧模拟地层反力，建立二维管片-接缝不连续模型和三维精细化管片-接缝不连续模型，模拟不同土质中（固结黏性土、硬质黏性土、中等程度黏性）盾构隧道上方不同加卸载水平下的结构变形、材料内力以及材料损伤变化规律，并讨论了螺栓异常工作对结构的影响，得到了不同土质中径向相对位移、接头张开量、材料应力和混凝土损伤因子关于加卸载量的关系曲线，及接头张开量、螺栓应力水平分别在预紧力损失和锈蚀深度两种异常状态的变化曲线.研究结果表明：从结构变形宏观指标给出了3种土质条件下加卸载的荷载安全值分别为510、340 kPa和170 kPa；从材料应力水平及损伤程度给出了加卸载的荷载安全值分别为340、170 kPa和170 kPa；螺栓预紧力损失对结构的影响主要受拱顶接头张开量控制，螺栓锈蚀对结构的影响主要受螺栓应力水平控制，且锈蚀深度的安全限值为6 mm.
：To study the effects of material damage and structural characteristics in a tunnel shield during loading and unloading, we conducted an investigation using a plastic-damage constitutive model for the concrete material, nonlinear contact theory, Python's secondary development, and a unidirectional compression spring around the shield circle, which represented the ground reaction force. A Two-dimensional (2D) discontinuous segment-joint model along with a three-dimensional (3D) precision discontinuous segment-joint model were built to simulate the tunnel shield's structural distortion and internal forces when exposed to varying material damage conditions during both loading and unloading. These conditions were explored using three different soil-condition scenarios. The influence of bolt abnormality on the structure is discussed, with graphs showing the corresponding soil radial displacement, the joint stretching value, material stress, and the damage factor for both the loading and unloading condition. Graphs for the joint stretching value and bolt stress levels are presented for two kinds of abnormalitiespre-tightening force loss and corrosion depth. The results show that the deformation index for the macro-structure given three kinds of soil conditions are 510, 340, and 170 kPa, which are considered safe values for loading and unloading. Regarding material stress level to avoid extensive damage, the safe values for loading and unloading are 340, 170, and 170 kPa. The influence of bolt preload loss on the structure is primarily controlled by the opening of the dome joint. The influence of bolt corrosion on the structure is primarily controlled by the stress level of the bolt. The safety limit for the corrosion depth is 6 mm