大直径盾构隧道单环结构安全性评价分析

Analysis on Safety Evaluation of Single-Ring Structures in Large-Diameter Shield Tunnels

为研究基于多项指标的大直径盾构隧道单环结构安全性能的评价方法,依托江阴靖江长江隧道建设工程,通过有限元模拟与现场实测数据结合对盾构隧道顶部加载过程中的结构失稳破坏过程进行研究,得到结构收敛变形和内力特征发展规律,选取收敛变形、钢筋拉应力、钢筋压应力、环向螺栓应力和纵缝张开量为评价指标并确定了各指标相关性,提出基于评价指标相关曲线的指标权重计算方法。结果表明:盾构隧道断面结构破坏过程可以依据结构内力关键节点值总结为弹性受力阶段、裂缝损伤缓慢发展阶段、大面积损伤发展阶段和加速失稳阶段;隧道断面地质条件对结构内力状态有一定影响,同一埋深下,砂土层隧道拱顶沉降远大于黏土层,且水压力对接头螺栓具有一定的保护作用;对评价指标分别进行健康状态分级,绘制内力指标与收敛变形的健康状态评估值关系曲线,通过最小二乘法拟合得到收敛变形、钢筋拉应力、钢筋压应力、环向螺栓应力、纵缝张开量的权重比例为0.48∶0.05∶0.23∶0.13∶0.11,初步建立了适用于大直径盾构隧道的单环结构安全性能评估计算公式。

This study proposed a method for evaluating the safety performance of single-ring structures in large-diameter shield tunnels using multiple indicators,with the Jiangyin-Jingjiang Yangtze River Tunnel as a case study.The structural instability and failure processes during loading on the top the tunnel were analyzed by combining finite element simulations with field measurement data.Key development patterns of structural convergence deformation and internal force characteristics were of reinforcement,compressive stress of reinforcement,circumferential bolt stress,and longitudinal joint opening were selected as evaluation indicators,and their correlations were determined.A method for calculating indicator weights based on the correlation curves of evaluation indicators was proposed.The results showed that the failure process of the shield tunnel cross-sectional structure could be divided into four stages based on the key values of structural internal forces:the elastic loading stage,the slow crack propagation stage,the large-scale damage progression stage,and the accelerating instability stage.Geological conditions at the tunnel cross-section affected the internal force state.Under the same burial depth,the settlement at the arch of the tunnel in sandy layers was much greater than in clay layers,and water pressure could offer some protection to joint bolts.The evaluation indicators were classified by health status,and a curve of the relationship between internal force indicators and the health assessment value of convergence deformation was plotted.Using the least squares method,the weight proportions of convergence deformation,tensile stress of reinforcement,compressive stress of reinforcement,circumferential bolt stress,and longitudinal joint opening were determined to be 0.48∶0.05∶0.23∶0.13∶0.11.A preliminary formula for assessing the safety performance of single-ring structures in large-diameter shield tunnels was established.