变高荷载下大型深隧管片衬砌裂损机理及三维数值流形法研究

Crack damage of lining is always one of the major failure modes of tunnels. In recent years, several large deep tunnels for water storage and drainage (LDTWSD) are being constructed or planned in some of China's most developed cities. These new-type LDTWSD differ from those traditional highway tunnels and subway tunnels in that their lining structures are required to withstand high internal water pressure. What is the crack damage characteristic of the segmental lining of an LDTWSD? Which parts are the most vulnerable ones to suffer from crack damage? And so on. These are becoming the emergent and important issues for security, quality and costs of construction as well as long-term maintenance costs regarding an entire LDTWSD project. To ensure the normal operation and function of an LDTWSD in the service life, the crack damage mechanism of the segmental lining is required to be clarified using appropriate methods and elaborate analyses..This study will resort to the full-scale segmental lining tests carried out in Tongji University and designed for the LDTWSD below Suzhou River, to find out the characteristic of the force, deformation and crack damage of the segmental lining under internal and external cyclic high-loading. On this basis, a new three-dimensional model will be proposed to describe the damage-crack-friction behavior of concrete under cyclic high-loading. Integrated with 8-noded hexahedral finite cover technique, contact theory and simplex integration scheme for arbitrary polyhedrons, the three-dimensional numerical manifold method (3-D NMM) will be developed to investigate and thus reveal the laws that govern two modes of crack damage of concrete under cyclic high-loading, i.e., flexural-tensile mode and flexural-compressive mode. The whole crack damage failure process of the segmental lining of the LDTWSD under internal and external cyclic high-loading will be presented using 3-D NMM simulation, and eventually the relevant crack damage mechanism will be clarified. In addition, this study will provide scientific fundamental and technical support for the segmental lining of the LDTWSD in terms of structure design and optimization and prevention from crack damage failure.

衬砌裂损是隧道的主要破坏形式之一。与传统的公路隧道、地铁隧道等不同，新兴的大型排蓄深隧承受高内水压，其管片衬砌的裂损特征究竟如何？哪些部位是较易裂损的薄弱环节？等等。这些是关乎大型排蓄深隧工程安全、质量、造价与维护费用的关键问题。为确保大型深隧的使用功能和寿命，需采用适当的方法分析阐明其管片衬砌的裂损机理。.本研究依托同济大学开展的苏州河段深层排水调蓄管道系统工程管片衬砌足尺试验，探明内外高压交变荷载作用下大型深隧管片衬砌受力变形裂损特征；基于此，建立高压交变荷载作用下混凝土三维损伤-断裂-摩擦模型，发展集成8节点六面体有限覆盖、任意多面体接触理论与多项式单纯形积分方案的三维数值流形法；揭示高压交变荷载作用下混凝土弯拉与弯压裂损规律；模拟内外高压交变荷载作用下大型深隧管片衬砌裂损破坏全过程，最终阐明其裂损机理；为大型排蓄深隧管片衬砌的设计优化及其裂损破坏的预测防治等提供科学依据和技术支撑。

本项目依托苏州河段深层排水调蓄管道系统工程试验段，开展复杂内外压力环境下深隧管片衬砌结构力学特性及变形裂损数值模拟研究。考虑到深隧管片衬砌结构的特点及受力特性，推导了真实坐标下的三维数值流形元法所有公式，将单元矩阵、接触矩阵和摩擦矩阵等矩阵进行组装后进行联立方程组求解，实现了任意多面体结构连续力学行为分析；提出了基于多面体局部凸分解方案的任意多面体进入体接触搜索方法，网格单元的拓扑形态更普适、更复杂，不限定为简单多面体，可以包括凸体、凹体、带孔洞多面体及其结合体等，适用于基于多面体网格的数值模拟方法的接触搜索与计算，包括但不限于非连续变形分析法、离散元法、有限元法和数值流形元法，实现了任意多面体结构接触计算与非连续力学行为分析；完善了裂隙网络切割及块体系统全空间拓扑识别方法，解决了对合边、非流形点等退化或奇异网络结构的拓扑识别与优化问题，实现了普适性的有限延展裂隙网络及同胚于N环面的块体系统识别，为三维数值流形元法有限覆盖动态切割与流形单元更新奠定了严格的理论与方法基础，基于此可实现任意多面体结构连续–非连续力学行为分析；将深入进行管片衬砌结构接触变形分析模型建模，开展单环力学性能、多环力学性能、内水压作用等对衬砌结构力学性能影响的数值模拟分析研究。