环形预应力锚索失效对高内压隧洞内衬应力的影响

The Influence of Loop Prestressed Anchor Cable Failure on Stress of Inner Lining in High Pressure Tunnel

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。

Failure of loop prestressed anchor cable is possible and indeed exists,which was affected by factors such as poor quality of construction,non-standard in anti-corrosion measures,excessive control tension for prestressed anchor cable and so on.In order to reveal the influence of loop prestressed anchor cable failure on stress of bonded prestressed tunnel lining,this paper took the Yellow River-crossing tunnel as the engineering background.Three-dimensional finite element method was utilized to simulate the stress distribution of tunnel lining.The influence of anchor cable failure at different location and different numbers of failed cables on stress of the inner lining in high pressure tunnel was analyzed on the premise that the prestress of failed anchor cable had totally lost.The results of the research show that the compressive stress decreases in the partial area near the failed anchor cable and the distribution of loop stress becomes nonuniform and some tensile stress areas appear.Anchor cable failure in the middle of the lining segment would lead to a larger affected area but less influence on compressive prestress.In contrast,anchor cable failure at the end of the lining segment would lead to a smaller affected area but more influence on compressive prestress.The maximum value of tensile stress exceeds the concrete tensile strength when the anchor cable at the end of the lining segment failed or both of two adjacent anchor cables failed in the middle of the lining segment,which would lead to concrete crack and do harm to the structure.