强震作用下可液化地基上核电厂防波堤大变形特性研究

Breakwater is an important earth structure of water-taken-drainage engineering for the coastal nuclear project. It is easy for the seabed foundation where liquefiable sand exists to liquefy under strong earthquake which will result in large deformation of breakwater. The unmaking waves function and water-taken-drainage function of the breakwater will be effected. It is of significant importance to obtain the deformation of the breakwater precisely for functional evaluation and seismic design. However, the large deformation induced by liquefaction foundation cannot be well simulated by the commonly used computation methods. In the program, a polygon element with good adaptability to deformation for saturated porous medium will be presented and the information mapping technique with high precision for a generalized plastic model of soils will be developed based on the scaled boundary finite element method and the generalized Biot’s dynamic consolidation theory, and a stable and high efficient large deformation computation method will be established and programmed firstly. Subsequently, shaking table model tests of breakwater and its foundation will be carried out. The deformation process of the model will be repeated and phenomena of the seismic damage in actual engineering will be reappeared numerically in order to validate the reliability of the computation method. Finally, systematic large deformation numerical simulations of practical engineering will be carried out to elaborately analyze the seismic response of the breakwater, the development pattern, physical mechanism and influence factors for the progressive failure and large deformation of breakwater will be illustrated. Then the economic and effective seismic measures will be recommended. This program has great theoretical and practical significances in aseismic design of coastal nuclear power plant breakwater.

防波堤是沿海核电厂取排水工程中重要的土工构筑物，当其海床地基存在可液化砂土时，强震条件下容易引发防波堤发生大变形，影响其防浪或取排水功能，准确获取防波堤变形进而评价其功能对抗震设计尤为重要。但是，目前常用的计算方法无法合理分析地基液化引发的大变形问题。鉴于此，本项目拟首先基于比例边界有限元理论和广义Biot动力固结理论，开发适应变形能力强的饱和多孔介质多边形单元，发展适用于土体广义塑性模型的高精度信息映射技术，建立稳定、高效的大变形弹塑性计算方法。然后，开展防波堤和地基的振动台模型试验研究，通过数值仿真重演模型变形过程并再现实际工程震害现象，验证计算方法的可靠性。最后，结合工程实例开展系统的大变形数值模拟，深入分析防波堤地震响应，探明防波堤动力大变形和渐进破坏的发展模式、物理机制及影响因素，建议经济、有效的抗震对策。本项目对沿海核电厂防波堤的抗震设计具有重要的理论意义和工程应用价值。

防波堤是沿海核电厂取排水工程中重要的土工构筑物，准确获取防波堤变形进而评价其功能对抗震设计尤为重要。本项目结合构筑物振动台模型试验，研究了地震响应特性及抗震性能，获得了其地震变形过程及破坏模式。在土体力学特性方面，通过主应力轴纯旋转试验，揭示了循环荷载作用下软弱地基土的软化特性，阐明了初始应力状态对土体在主应力轴耦合旋转下的孔压增长及变形的影响机制。在数值计算方法层面，基于比例边界有限元理论和广义Biot动力固结理论，引入两套高斯点并建立了相应比例边界多边形单元的平衡方程，将比例边界有限元法拓展至饱和土非线性分析。在数值模拟层面，开发了复杂耦合比例边界有限元法-有限元法（SBFEM-FEM）网格自动剖分、识别、计算模型生成以及数值仿真的精细化分析系列软件并应用，重演模型变形过程并再现已有试验结果，验证了广义塑性模型及数值计算方法的可靠性。最后，结合我国实际核电工程，采用本项目建立的方法研究了防波堤工程中地基液化、变形规律以及抗震能力，并从可靠度的角度分析了强震作用下核电工程土工构筑物的抗震安全性以及加固措施的作用效应。