The presence of voids or lining thinning directly affects the mechanical behavior of linings, and these defects threaten the safety of tunnel operation. In this study, a series of 1/5-scale model tests was used to investigate the mechanical behavior of normal concrete (NC) linings in consideration of voids and combined defects. Test results showed that the void and combined defects substantially reduced the load-bearing capacity and deformation properties of the linings. The inelastic mechanical behavior of the linings was also significantly affected by the defects. The effects of lining defects located at the spandrel were slightly weaker than those of lining defects located at the crown. As the void size or degree of combined defects increased, the tensile strain at the location of the lining defects also increased. Therefore, the defect position of the linings was easily damaged. The defects considerably reduced the overall deformation of the linings but increased the local deformation. The distribution of lining cracks was concentrated at the defect position. In addition, different failure characteristics of the lining were observed due to the differences in defects.

中文翻译：

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考虑空隙和衬里减薄的数控衬里力学行为的实验研究

空隙或衬砌变薄的存在直接影响衬砌的机械性能，这些缺陷威胁到隧道作业的安全性。在这项研究中，一系列的1/5比例模型测试用于研究普通混凝土（NC）衬砌的机械性能，其中考虑了空隙和组合缺陷。试验结果表明，空隙和结合缺陷大大降低了衬砌的承载能力和变形性能。衬里的非弹性机械性能也受到缺陷的影响。位于翼梁上的衬里缺陷的影响比位于冠部的衬里缺陷的影响稍弱。随着空隙尺寸或结合缺陷程度的增加，衬里缺陷位置处的拉伸应变也增加。因此，衬里的缺陷位置很容易损坏。缺陷大大减少了衬里的整体变形，但增加了局部变形。衬里裂纹的分布集中在缺陷位置。另外，由于缺陷的差异，观察到了衬里的不同破坏特性。