基于损伤-断裂准则的水工混凝土结构水力劈裂数值模型

Many hydraulic concrete structures, such as high concrete dams, running perennially in the high pressure and high stress condition, are prone to hydraulic fracturing failure. The project intends to adopt physical test, theoretical analysis and numerical simulation methods to carry out the research. The large thermo-hydro-mechanical coupling triaxial test system is developed to carry out the hydraulic fracturing test of hydraulic concrete structure. So the whole process of concrete structure damage crack, crack propagation and failure under the high water pressure is studied. Then, combining the theory of meso - damage mechanics and macro - fracture mechanics, the concrete damage-fracture (D–K) criterion considering the seepage effect was proposed on the basis of experimental results and theoretical derivation. Finally, hydraulic fracturing numerical model of hydraulic concrete structure based on damage - fracture criterion is built. The hydraulic fracturing evolution mechanism of the hydraulic concrete structure under the action of high water pressure will be revealed. The project has two main innovation points. Firstly, the concrete damage - fracture criterion considering the seepage effect is put forward. Secondly, the hydraulic fracturing numerical model of hydraulic concrete structure based on damage -fracture criterion is established. The project aims to provide theoretical foundation and basis for structure safety evaluation of high concrete dams.

高混凝土坝等水工混凝土结构常年在高水压、高应力条件下运行，易发生水力劈裂破坏。本项目拟采用物理试验、理论分析和数值模拟等方法，利用研制的水-固-热耦合大型三轴试验系统进行水工混凝土结构水力劈裂试验，研究高水压作用下水工混凝土结构损伤起裂、裂缝扩展至失稳破坏过程；结合细观损伤力学和宏观断裂力学理论，综合试验结果和理论推导，提出考虑渗流作用的混凝土D-K损伤断裂准则；建立基于损伤-断裂准则的水工混凝土结构水力劈裂数值模型，揭示高水压作用下水工混凝土结构水力劈裂破坏的演化机理。项目创新主要包括：提出考虑渗流作用的水工混凝土D-K损伤断裂判定准则；建立基于损伤-断裂准则的水工混凝土结构水力劈裂数值模型。该项目旨在为水工混凝土结构的安全评价和运行维护提供理论依据。

高混凝土坝等水工混凝土结构常年在高水压、高应力条件下运行，易发生水力劈裂破坏，而水工混凝土结构水力劈裂形成和破坏演化机理复杂。本项目基于混凝土材料和水泥砂浆两种试件，开展了单轴受压、双轴受压、四点弯曲弯矩等条件下的水力劈裂试验，研究了不同应力状态、荷载施加方式、初始裂缝开度和深度、化学侵蚀溶液溶度和历时等对试件水力劈裂破坏过程的影响，分析了裂缝扩展路径上缝内水压演化规律，推导了缝内水压力的计算公式，结合渗流力学和断裂力学理论，提出水力劈裂裂缝扩展的损伤断裂准则，考虑缝内水流与结构变形的耦合效应，建立水力劈裂数值分析模型。结果表明，在缝内水压和轴压作用下，试件裂缝尖端会产生应力集中，使得临界劈裂水压与轴压的差值小于其劈拉强度；试件临界劈裂水压值与试件劈拉强度、轴压均呈线性关系。双轴受压状态下水力劈裂试验试件破坏类型为非完全水力劈裂破坏，破坏造成的裂缝细微，未形成完全贯通试样的连续裂缝。四点弯曲弯矩作用下，裂缝发展过程中的混凝土试件应变可分为线性段及指数段，当应变进入指数段时，试样临近破坏。较小的荷载增量即会打破稳态，促使裂缝失稳扩展。劈裂水压与拉应力存在叠加效应，若最值作用位置相同，裂缝尖端应力集中现象明显，易引起水力劈裂破坏。不同化学溶液侵蚀下，试件起裂临界水压力和劈裂临界水压力随侵蚀时间的演化规律一致，均具有明显的时间依赖性和阶段性。通过楔形劈裂试验算例和单裂缝水力劈裂算例数值模拟，论证了数值分析模型的合理性，模拟某高重力坝水力劈裂破坏过程。项目研究成果有效推动水工混凝土结构水力劈裂数值模型研究，可为水工程的安全评价和长效运行维护提供理论依据。