基于安全度的黄土隧道结构承载性能分析

Analysis of Structural Bearing Property of Loess Tunnel Based on Safety Degree

基于八仙峁隧道、麻塌隧道2组典型断面二衬混凝土应变监测数据,分析了二衬混凝土在黄土隧道中应变随时间的变化规律;通过换算得到二衬结构所受应力,将换算结果代入安全度应力表达式,得出该断面下黄土隧道二衬安全度分布,并与有限元数值模拟结果进行对比。结果表明:在黄土隧道的支护结构中,二衬混凝土结构不仅作为安全储备,而且往往需要承受大部分荷载,通过数值模拟确定二衬承受的荷载约为围岩荷载的40%;二衬混凝土结构作为受压构件,其最大应变出现在边墙底部位置;数值模拟与计算所得二衬安全度分布规律基本一致,拱顶、拱肩、边墙底部仰拱部位安全度相对较小但满足规范要求,仰拱底部所受压应力最大且安全度未满足规范要求。

Based on the two groups of strain monitoring data of the secondary lining concrete for Baxianmao tunnel and Mata tunnel, the strain change law of secondary lining concrete in loss tunnel with time was analyzed. The stress of secondary lining structure was obtained by converting, then the conversion results were substituted into the stress expression of safety degree, and the distribution of secondary lining safety degree of loess tunnel was obtained. Furthermore, the results were compared with the finite element numerical simulation results. The results show that secondary lining concrete structure is not only a safety reserve in loess tunnel support structure, but also bears most of loads of structures. Numerical simulation results prove that the stress on secondary lining is as 40 % as total stress from wall rock. The secondary lining concrete structure acts as a compression member and the peak value of strain is at the bottom of side wall. The numerical simulation results is consistent with calculation results. The safety degrees of crown, spandrel, inverted arch of side wall bottom are relatively small, but can meet the requirements of specifications, while stress of inverted arch bottom is maximal, and the safety degree can not meet the requirements of specifications.