针对高地应力环境下西部艰险山区隧道频发的软岩挤压大变形问题，传统基于“强支硬顶”理念的刚性支护结构常因围岩大变形而发生开裂、钢架扭曲甚至失稳破坏。为控制高地应力下软岩大变形导致的二次衬砌开裂和破坏，提高隧道的长时防灾适应性，提出“增韧初期支护-高聚物缓冲层-二次衬砌”的刚柔复合衬砌结构，探明刚柔复合衬砌在挤压大变形条件下的承载特征；研究基于自主研发的隧道衬砌加载试验装置，针对传统复合衬砌和不同厚度的刚柔复合衬砌开展大缩尺比模型加载试验，通过数字图像相关分析与声发射技术监测衬砌应变演化及裂缝发展过程，并对比分析试件的受力变形特征、损伤破坏模式、承载和变形能力等。试验结果表明： 1）与传统复合衬砌相比，刚柔复合衬砌在承载能力、变形能力和韧性方面分别提升188%、21%和115%； 2）刚柔复合衬砌构建“增韧初期支护-高聚物缓冲层-二次衬砌”协同作用体系，高聚物缓冲层对衬砌的让压能力具有显著影响； 3）刚柔复合衬砌的损伤演化呈现初期支护开裂、裂缝扩展、缓冲层压缩和破坏4个阶段渐进特征。
Large squeezing deformation of soft rocks occurs frequently in tunnels constructed in complex mountainous areas under high ground stress. Conventional rigid support structures typically crack, experience steel arch distortion, or fail because of the large deformation of surrounding rock. In this study, a rigid-flexible composite lining structure with a toughened primary support-polymer buffer layer-secondary lining is proposed to control the cracking and damage of the secondary lining and improve long-term disaster prevention adaptability. The load-bearing characteristics of the proposed rigid-flexible composite lining under large squeezing deformation are clarified. Subsequently, large-scale model loading tests are conducted for conventional and rigid-flexible composite linings with varying thicknesses. These tests are based on an independently developed tunnel lining loading test device. Finally, the strain evolution and crack development are monitored using digital image correlation and acoustic emission techniques, and the force-deformation characteristics, damage failure modes, and load-bearing and deformation capacities of the specimens are compared and analyzed. The test results demonstrate that (1) compared with conventional composite lining, the load-bearing capacity, deformation capacity, and toughness of the proposed rigid-flexible composite lining increase by 188%, 21%, and 115%, respectively; (2) the polymer buffer layer in the built synergistic system of toughened primary support-buffer layer-secondary lining in the proposed rigid-flexible composite lining exhibits a notable impact on the yielding capacity of the lining; and (3) the damage evolution of the rigid-flexible composite lining presents a four-stage progressive characteristic of primary support cracking, crack propagation, buffer layer compression, and failure.
