为明确衬砌脱空与欠厚组合缺陷对隧道结构的影响，建立衬砌欠厚和背后脱空组合缺陷的三维有限元数值模型，研究衬砌组合缺陷不同参数（缺陷尺寸、位置）对其结构变形、内力及安全性的变化规律。研究结果表明： 1）衬砌脱空及欠厚组合缺陷重构围岩-衬砌应力场，导致拱顶原受压侧由压应力转为拉应力且缺陷边缘应力集中现象加剧。当缺陷尺寸增大到临界值（纵向缺陷长度L≥6 m或欠厚比δ≥2/5）时，衬砌变形较无缺陷时增幅超200%，而多缺陷耦合（拱顶+双侧拱腰）引发内力非对称响应，位移增幅达53%。2）衬砌脱空及欠厚组合缺陷引发内力重分布，使弯矩极值增至无缺陷的3.1倍，轴力衰减至38%~53%，多缺陷耦合工况下拱肩弯矩增幅达104%，而单一缺陷增幅仅为50%~70%。3）衬砌脱空及欠厚组合缺陷显著降低截面安全系数，当缺陷尺寸增大到临界值（脱空范围α＞34°或欠厚比δ≥2/5）时，衬砌截面环、纵向安全系数降幅分别达40%~60%和60%~70%，单一缺陷降幅则通常小于40%，且临界值较单一缺陷显著降低。

To clarify the impact of combined defects of lining voids and insufficient thickness on tunnel structures, a three-dimensional finite element numerical model is established to simulate the combined defects of lining insufficient thickness and behind-lining voids. The study investigates the variation patterns of structural deformation, internal forces, and safety performance under different parameters (defect size and location). The results indicate the following: (1) The combined defects of lining voids and insufficient thickness reconstruct the surrounding rock-lining stress field, causing the originally compressed side at the crown to transition from compressive stress to tensile stress, while stress concentration at defect edges intensifies. When the defect size increases to a critical value (longitudinal defect length ≥ 6 m or insufficient thickness ratio ≥ 2/5), the lining deformation increases by over 200% compared to the defect-free condition. Moreover, multi-defect coupling (crown + bilateral haunches) induces asymmetric deformation, with displacement variations reaching 53%. (2) The combined defects trigger internal force redistribution, increasing the extreme bending moment to 3.1 times that of the defect-free condition, while axial force decreases to 38%－53%. Under multi-defect coupling conditions, the bending moment at the spandrel increases by 104%, whereas the increase under single-defect conditions is only 50%－70%. (3) The combined defects significantly reduce the sectional safety factor. When the defect size reaches a critical value (void range > 34° or insufficient thickness ratio ≥ 2/5), the circumferential and longitudinal safety factors of the lining section decrease by 40%－60% and 60%－70%, respectively. In contrast, the reduction under singledefect conditions is typically less than 40%, and the critical value is notably lower than that for single defects.