Abstract: It is not clear how to determine the flexural performance of reinforced structure and load sharing between old and new structures after composite arch is used to reinforce the cracked lining of tunnel. Taking the medium damage (the crack depth reaching 1/3 lining thickness) in the vault of local lining as the research object, the full-scale test by prefabricating crack of the original lining was adopted. The bending resistance test about the crack lining strengthened by the complex set of arch was carried out and the deformation of reinforced structure, the variation rule of cross-sectional bending stiffness changing with the load and the failure mode were analyzed.Combined with the test data, the distribution principle of the reinforcement structure load and the calculation method of the bending capacity were discussed. The tests show that: when medium-damage lining is reinforced with composite arches, ①the new and old structures share the load and deformation together before the existing cracks of the original lining are penetrated; the load after the penetration is mainly carried by the new arch; ②the newly added arches are evenly distributed and not extended to the original lining, which effectively improves the waterproof performance of the tunnel; ③the short-term stiffness of the reinforced structure can take the sum of the short-term stiffness of the original lining and the new arch; when the external load changes little, the internal force and the design reinforcement parameters can be calculated according to the stiffness distribution principle; ④the reinforced structure is subjected to bending failure load, which is consistent with the damage load of the newly added arches under the individual force; when the external load changes greatly, the reinforcement parameters should be designed according to the additional force of the new arch. The test results verify the reinforcement effect of the composite arch to a certain extent, and the calculation conclusions of load distribution and bearing capacity can be used as reference for the reinforcement design.

Key words: tunnel engineering, reinforcement, composite arch, full-scale test, crack lining, flexural behavior

摘要： 隧道裂损衬砌采用复合式套拱加固后，补强结构的抗弯性能及新旧结构分担荷载如何确定还没有定论。以中等破损(裂缝深度达1/3衬砌厚度)的拱顶局部衬砌为研究对象，采用足尺试验和原衬砌预制裂缝的方案，开展裂损衬砌经复合式套拱加固后的抗弯性能试验，分析补强结构变形、截面抗弯刚度随荷载的变化规律及其破坏模式，并结合试验数据对加固结构荷载的分配原则、受弯承载力计算方法进行探讨。试验表明：中等破损衬砌采用复合式套拱加固时，①原衬砌既有裂缝贯通前新旧结构共同分担荷载、协同变形，贯通后荷载主要由新增套拱承担；②新增套拱裂缝分布较均匀，且未扩展至原衬砌，有效改善了隧道防水性能；③加固结构短期刚度可取原衬砌、新增套拱各自短期刚度之和，外荷载变化不大时可按刚度分配原则计算内力、设计加固参数；④加固结构受弯破坏荷载与新增套拱单独受力的破坏荷载一致，外荷载变化较大时，宜按新增套拱单独受力设计加固参数。试验成果一定程度验证了复合式套拱的加固效果，荷载分配及承载力计算结论可供加固设计参照。

关键词: 隧道工程, 加固, 复合式套拱, 足尺试验, 裂损衬砌, 抗弯性能