Advanced computational geomechanics for analysis of earth structures

土工[地震]工程建模的未来将完全是基于性能的设计，即PBD，本质上是基于土体结构的位移。PBD和屈服后行为的评估需要向基于位移或变形的设计范式转变，而不是应用于土力学和基础工程问题的传统基于力的设计。非线性材料在不规则地震荷载作用下的真实感三维模拟是非常复杂的。为此，人们需要先进而高效的计算工具。这类工具需要处理岩土工程中的一些关键模型点，如瞬变荷载、用于真实产生和消散超孔压的完全耦合的固液相互作用、三维分析、结构单元的包含以及土基的本构关系，这是成功的数值模拟的关键部分。本提案的长期目标是将建模提高到一个新的水平，并向研究界和工程界提供更新和更准确的分析手段。本文将重点介绍砂土和粘土在地震荷载作用下的高级本构模型，以及三维框架下的数值模拟。本文的研究成果将为岩土材料循环加载的数值模拟提供两种新的本构模型。从校正和结果解释的角度来看，这些本构模型将是高效和严格的，但从校准和结果解释的角度来看，它是简单和用户友好的。新开发的模型将被有效地整合到FLAC3D计算框架中，这将扩大它们在高级研究社区和设计实践中的适用性。将使用UBC、NGI、NEES和C-Core提供的实验数据进行广泛的核实和确认。最后，在所开发的工具的应用方面，在众多相关问题中，将侧重于土-桩相互作用问题的分析，地震事件下结构性粘土中海底稳定性的研究，以及大坝三维表征的基本问题。

The future of modeling in Geotechnical [Earthquake] Engineering will be all about Performance-Based Design, PBD, essentially displacement based for earth structures. PBD and the evaluation of post-yield behavior require a paradigm shift toward a displacement or deformation-based design, as opposed to the traditional force-based design that has been applied to soil mechanics and foundation engineering problems. A realistic 3D simulation of the nonlinear material subjected to irregular earthquake loading is very complex. For this purpose, one needs advanced and efficient computational tools. Such tools need to handle a number of key modeling points in geotechnical engineering such as transient loading, fully coupled solid-fluid interaction for realistic generation and dissipation of excess pore pressure, three-dimensional analyses, inclusion of structural elements, and constitutive behavior of the soil matrix, which is the crucial part of a successful numerical simulation. The long-term aim of the present proposal is to bring the modeling to the next level, and to provide newer and more accurate means of analysis to the research and engineering communities. The focus here will be given to advanced constitutive modeling of sands and clays in seismic loading, and numerical simulation in 3D framework. The proposed research outcome would generate two novel constitutive models for numerical simulation of cyclic loading in geomaterials. These constitutive models will be efficient and rigorous, yet simple and user friendly from the perspective of calibration and interpretation of results. The newly developed models will be efficiently integrated into the FLAC3D computational framework, which will extend their applicability in the advanced research community and design practice. An extensive verification and validation will be conducted using the experimental data available at UBC, NGI, NEES and C-Core. Finally, on application of the developed tools, among many relevant problems, focus will be given to analysis of soil-pile interaction problems, study on ocean floor stability in structured clays under seismic events, and underlying issues in 3D characterization of dams.