Multidimensional constitutive and numerical modeling in geotechnical seismic analysis and design

岩土地震工程建模的未来将几乎完全基于基于性能的抗震设计理念。PBSD需要向基于位移或变形的设计转变，而不是传统的基于力的设计。它比传统的分析和设计方法更合理，并导致更节省成本的建设或更安全的设计。PBSD要求计算变形的可靠性有足够的度量。不规则地震荷载作用下岩土结构变形的真实模拟是非常复杂的。模拟工具应基于有效应力公式、完全耦合的固体-孔隙流体相互作用以及用于处理大型问题的并行/云计算功能来处理3D动态分析。最重要的问题是适当的本构模型的土壤基质。目前在工程实践中使用的土壤模型不包括许多非常重要的因素，影响应力-应变关系。解决地震的多方向循环荷载也是极具挑战性的。从与主要从业者（如处理土坝的BC Hydro）的讨论中可以看出，他们主要关注的是可用的不同模型给出的不同响应;在某些情况下，这些差异足以引起极大的关注。 拟议的研究将解决几个具有挑战性的方面的本构和数值模拟砂，粉土和粘土在复杂的多方向加载。将收集和详细研究一系列相关的实验室元素测试数据。这些信息将用于开发砂、粉土和粘土的多方向循环加载的几种新型本构建模功能。重点将是开发具有零弹性范围的SANISAND-Z模型，改进多方向加载的固有和演变结构，并提供液化后大剪切变形的积累。此外，率依赖的重要特征将被添加到最近开发的SANICLAY-B模型。开发的模型将在FLAC 3D，OPENSEES和/或DIANA中稳健地实施。模型和开发的工具将被广泛验证和确认使用元件测试和离心测试结果。在应用方面，在许多相关问题中，重点将是非常具有挑战性和重要的问题：（i）多维地震场地反应分析，（ii）土坝的地震变形分析，它给出了极端事件中的超高损失，以及研究大坝稳定性补救措施的有效性。开发的建模工具和模拟导致重新审视传统的地震分析和设计与PBSD，这是显着的相关性，以减少地震风险在加拿大。

The future of modeling in geotechnical earthquake engineering will be based almost exclusively on Performance-Based Seismic Design philosophy. PBSD requires a paradigm shift toward a displacement or deformation-based design as opposed to the traditional force-based design. It is more rational than the conventional analysis and design methods, and leads to more cost effective construction or safer design. PBSD demands an adequate measure of reliability of computed deformations. A realistic simulation of deformation of geo-structures subjected to irregular earthquake loading is very complex. The simulation tools should handle 3D dynamic analysis based on effective stress formulation, fully coupled solid-pore fluid interaction, and parallel/cloud computing features for handling large problems. The most important issue is proper constitutive modeling of the soil matrix. Current soil models used in engineering practice do not include many of the very important factors that affect the stress-strain relationship. It is also extremely challenging to address multidirectional cyclic loading of earthquakes. From discussion made with major practitioners, such as BC Hydro who deal with earth dams, it becomes clear that their main concern is with the different responses given by the different models that are available; in some cases these differences are significant enough to cause great concern. The proposed research will address several challenging aspects of constitutive and numerical modeling of sand, silt, and clay under complex multidirectional loading. A series of related laboratory element test data will be collected and studied in detail. The information will be used in development of several novel constitutive modeling features for multidirectional cyclic loading of sands, silts and clay. The highlight would be on development of the SANISAND-Z model with zero elastic range, refined inherent and evolving fabric for multidirectional loading, and provisions for accumulation of large post-liquefaction shear deformation. Also the important feature of rate-dependency will be added to the recently developed SANICLAY-B model. The developed models will be robustly implemented in FLAC3D, OPENSEES and/or DIANA. The models and developed tools will be extensively verified and validated using element test and centrifuge test results. On the application side among many relevant problems focus will be given to the very challenging and important problems of (i) multidimensional seismic site response analysis, and (ii) seismic deformation analysis of earth dams, which gives the loss of freeboard in extreme events, and also study of the efficiency of remedial measures for the dam stability. The developed modeling tools and simulations lead to revisiting conventional seismic analysis and design with PBSD, which is of significant relevance to the reduction of seismic risk in Canada.