软弱围岩中的新型双层复合衬砌的受力特性研究及渗水风险分析

 某输水隧洞位于河床的软弱砂岩中，其双层复合预应力衬砌结构形式新颖，受力条件复杂。为了解这种新型双层复合预应力衬砌的工作性态和受力特性，分别采用现场1∶1仿真模型试验方法、三维非线性有限元数值分析方法，并将数值分析结果与仿真试验进行对比分析。有限元分析按照仿真模型试验中管片拼装、分层填土、内衬浇筑、内衬预应力张拉以及内衬充水加压的实际过程模拟，计算中考虑衬砌与土体的耦合效应，通过外衬变形反分析调整土体计算参数，采用基于直接约束的接触迭代算法模拟管片与管片之间、内衬与外衬之间的多重接触与传力。研究结果显示，无论是结构变形、缝隙开度还是结构应力，有限元分析与仿真试验规律一致，数值接近，两种方法相互验证了这种具有多重复杂接触边界的非连续变形柔性结构的受力特性，明确了内、外衬的传力机制；在此基础上，进一步分析高压内水外渗对结构安全性的影响以及预防措施，其研究成果可供类似工程参考。

MECHANICAL CHARACTERISTICS AND SEEPAGE RISK ANALYSIS OF DOUBLE COMPOSITE LININGS IN SOFT SURROUNDING ROCKS

A water diversion tunnel is located in the soft surrounding rocks，and double composite linings are employed during tunnel structure. In order to reveal the mechanical properties of such prestressed double composite linings，the 1∶1 simulation model test and 3D nonlinear finite element method are used. The test processes，including segments assembling，earth filling by layer，inner lining casting，pretension of inner linings，and applied water pressure，are simulated in sequence in the finite element model. Besides，the coupling effects of lining and earth are also taken into consideration. The earth parameters are determined by back analysis method with the displacement of outer lining. The contact between the assembled segments and the inner or the outer lining is also simulated by contact algorithm based on direct control method. The results of finite element method match well with test results，such as displacement and stress of structure，opening of gap. Furthermore，the seepage rise is discussed and corresponding measures are proposed. The results are helpful for the design of similar engineering projects.