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地震设计理念。PBSD要求从传统的基于力的设计转向基于位移或变形的设计。它比传统的分析和设计方法更合理，并导致更经济有效的施工或更安全的设计。PBSD要求对计算变形有足够的可靠性。不规则地震荷载作用下土工结构变形的真实模拟是非常复杂的。仿真工具应处理基于有效应力公式、完全耦合固-孔-流体相互作用以及并行/云计算特征的三维动态分析，以处理大型问题。最重要的问题是正确的土基质本构模型。目前工程实践中使用的土体模型没有包括许多影响应力-应变关系的重要因素。处理地震的多向循环载荷也是极具挑战性的。从与主要实践者的讨论中，例如处理土坝的卑诗水电公司，很明显，他们主要关心的是不同可用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。***拟议的研究将解决复杂多向加载下砂、粉土和粘土本构和数值模拟的几个具有挑战性的方面。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、粉砂和粘土多向循环加载的几种新型本构模型特征。重点将是SANISAND-Z模型的开发，该模型具有零弹性范围，改进了多向加载的固有和不断发展的结构，并提供了液化后大剪切变形的积累。此外，最近开发的SANICLAY-B模型也将添加速率依赖的重要特性。开发的模型将在FLAC3D、OPENSEES和/或DIANA中健壮地实现。模型和开发的工具将使用元件测试和离心机测试结果进行广泛的验证和验证。在应用方面，在众多相关问题中，重点讨论了极具挑战性和重要性的问题：(1)多维地震场址反应分析；(2)土坝地震变形分析，它给出了极端事件下的干舷损失；以及大坝稳定补救措施的有效性研究。开发的建模工具和模拟使PBSD重新审视了传统的地震分析和设计，这对降低加拿大的地震风险具有重要意义

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.**