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受施工质量不良、防腐措施不规范、锚索张拉控制应力过高等因素的综合影响,环形预应力锚索存在失效的可能与现实。为揭示高内压隧洞内衬中环形预应力锚索破坏失效后对隧洞内衬应力的影响,以南水北调中线穿黄隧洞工程为例,采用三维有限元方法对隧洞内衬结构的应力分布进行模拟计算,假设标准段衬砌中不同部位、不同根数锚索的预应力完全失效,分析其对隧洞内衬应力的影响。研究结果表明,锚索失效后失效锚索附近局部区域预压应力减小,运行中的环向应力分布均匀性变差并出现了拉应力区;衬砌段中部锚索失效对内衬应力的影响区域较大但对应力值的影响较小,端部锚索失效对内衬应力的影响区域较小,但对应力值的影响较大;端部锚索失效和中部相邻两根锚索同时失效时的运行工况最大拉应力值超过混凝土设计抗拉强度,将引起混凝土的局部开裂,可能导致结构破坏。
Due to the comprehensive influence of poor construction quality, non-standard anti-corrosion measures and over-tensioning of anchor cables, the possibility and reality of failure of annular prestressed anchor cables exist. In order to reveal the influence of the failure of prestressed annular cable in high internal pressure tunnel lining on the stress of tunnel lining, taking the Yellow River Tunnel Project of the Middle Route of South-to-North Water Transfer Project as an example, the stress distribution of the tunnel lining structure is simulated by the three-dimensional finite element method It is assumed that the prestressing force of different numbers of anchor cables in different sections of the standard section lining completely fails and the influence on the stress of tunnel lining is analyzed. The results show that the prestressed stress in the local area near the failure anchor cable decreases after failure, and the uniformity of the circumferential stress distribution in operation deteriorates and the tensile stress zone appears. The influence of anchor failure in the middle of the lining section on the lining stress But the impact on the stress of lining is smaller, but the influence on the stress value is larger; the failure of the end anchor cable and the simultaneous failure of the two anchor cables in the middle Failure of the operating conditions maximum tensile stress exceeds the tensile strength of concrete design will cause local cracking of concrete, which may lead to structural damage.