混凝土盾构隧道衬砌裂损演化及断裂破坏特性研究

Concrete shield tunnel linings may contain cracks and defects because of the complex surrounding environment, and these cracks and defects will have a bad influence on the lining and weaken its bearing capacity, thus shortens its life span. All the common numerical methods have great trouble in dealing with crack problems for complex three-dimensional structures, and little research has been done in the fracture analysis of concrete shield tunnel linings so far. This project takes cracked concrete shield tunnel lining as research object, and makes comprehensive use of theoretical analysis, computer programming, numerical simulation and laboratory loading test to carry out the following research: To develop and improve the Symmetric Galerkin Boundary Element Method (SGBEM) for fracture analysis. To study the alternating algorithm between SGBEM and FEM, and develop the SGBEM-FEM Alternating Method program. To carry out a three-dimensional numerical experiment and laboratory loading test on cracked concrete linings by employing SGBEM-FEM Alternating Method, and study the lining’s bearing capacity and deformation, finally obtain the propagating law of existing defects in the lining and its ultimate condition and failure model. This study can help to build a three-dimensional fracture mechanics model of cracked concrete shield tunnel lining which accords with engineering practice better, and provide significant reference value for practical engineering in shield tunnels.

混凝土盾构隧道衬砌由于赋存环境复杂会产生各种裂损缺陷，这些裂损缺陷影响衬砌正常使用并削弱其承载性能，缩短衬砌的安全寿命。现有数值方法对复杂三维结构进行断裂破坏分析时存在很大困难，当前针对混凝土盾构衬砌断裂破坏的研究还比较少。本项目以带裂缝混凝土盾构衬砌为研究对象，综合运用理论推导、计算机编程、数值试验和室内荷载试验相结合的手段，开展如下关键内容研究：发展结构断裂破坏分析的三维对称伽辽金边界元法（SGBEM）；研究SGBEM和有限元法（FEM）迭代算法理论，开发SGBEM-FEM迭代算法通用程序；借助SGBEM-FEM迭代算法开展带裂缝混凝土盾构衬砌断裂破坏三维数值试验和室内荷载试验，研究裂损衬砌的承载性能和位移变形，获得衬砌已有裂损缺陷的演化发展规律以及裂损衬砌的极限状态和最终破坏模式。项目成果可建立更符合工程实际的混凝土盾构衬砌三维断裂力学模型，并为盾构隧道实际工程提供重要参考价值。

立足土木工程地下结构计算理论和试验技术学科前沿，本项目以带裂缝等缺陷的混凝土盾构衬砌管片为研究对象，综合运用理论分析与推导、计算机编程、数值试验和室内荷载试验相结合的手段，开展了如下关键内容研究：发展了结构断裂破坏分析的三维对称伽辽金边界元法，研究三维对称伽辽金边界元法和有限元法迭代算法理论，并在此基础上基于C++编程语言开发了三维对称伽辽金边界元-有限元迭代算法基本程序。数值算例表明该方法可以精确计算三维结构复杂裂纹的应力强度因子，并能有效模拟初始裂纹在疲劳荷载作用下的扩展直至结构破坏全过程，利用该方法估算的结构疲劳寿命和已有试验结果十分接近，该方法在分析复杂三维裂纹时只需花费极少人力物力，并具有精度好，效率高等优点。结合南京地铁5号线典型工程，借助三维对称伽辽金边界元-有限元迭代法开展了带裂缝混凝土盾构衬砌管片断裂破坏三维数值试验和室内荷载试验，研究了裂损衬砌的承载性能和变形特性，获得了衬砌已有裂损缺陷的演化发展规律以及裂损管片的极限状态与最终破坏模式。研究表明，盾构管片在常见荷载作用下的断裂属于混合型断裂，并由I型断裂主导；加载方式和偏心距对衬砌管片的承载力影响很大，正弯矩加载管片的承载力远大于受负弯矩作用管片的承载力，而同等情况下偏心距越大则管片的承载力越小；在疲劳荷载作用下，偏心距较大时管片的初始裂纹最终发展为整体贯穿型裂纹，对隧道安全性危害极大；而偏心距较小时初始裂纹最终形成局部裂纹，危害相对较小，因此对盾构隧道衬砌结构而言，大偏心比小偏心更危险。本项目建立了更符合工程实际的混凝土盾构衬砌三维断裂力学模型，可为盾构隧道实际工程提供参考价值。