Deformation-Based Seismic Analysis and Design of Waterfront Retaining Structures

滨水结构包括重力墙、板桩墙和桩基码头等，这些结构对强震的响应主要取决于复杂的土-结构-地基相互作用以及地基和回填土的不排水特性。目前这种系统的设计理念旨在将支承结构的变形限制在可接受的水平。根据它们的重要性和功能，本研究的目的是发展一种基于变形的分析方法，用于滨水结构的抗震评估和设计。研究典型的二维重力墙和板桩墙在超孔压积聚和液化作用下的抗震性能和破坏情况。各种地基处理技术的表现，以预测的永久变形为判据，对不同水平的地面震动强度进行预测，将为治理优化提供指导。将使用有效应力、非线性有限元方法和边界元相结合的方法来精确模拟通过出射波的能量辐射。地基、回填土和近场土采用严格、有效的临界态模型，可以预测砂土的密实度、孔压积累、液化和循环移动性。该数值模型能较好地模拟超孔隙水压力的产生、再分布和消散过程，揭示可能导致破坏的变形机理。调查将与来自日本清水公司和希腊NTUA的研究人员密切合作进行。这是一项由NSF 98-36“美日城市地震减灾研究”第二年计划资助的奖项。

Waterfront structures include gravity walls, sheet pile walls, and pile supported wharfs which are vulnerable to earthquake damage the response of such structures to strong ground shaking depends primarily on the complex soil-structure-foundation interaction and the undrained behavior of the foundation and backfill soils. Current philosophy in the design of such system aims at limiting deformations of the supported structures to acceptable levels. Depending on their importance and function.The objective of this research is to develop a deformation-based method of analysis for the seismic evaluation and design of waterfront structures. The seismic behavior and damage of typical two-dimensional gravity walls and sheet pile walls that are vulnerable to excess pore water pressure buildup and liquefaction, will be investigated. The performance of various ground improvement techniques using as criterion the predicted permanent deformation for different levels of ground shaking intensity and will provide guidelines for remediation optimization. An effective-stress, nonlinear finite element method, coupled with boundary elements for accurate modeling of the energy radiation through outgoing waves will be used. The foundation, backfill and near-field soils are modeled with a rigorous, efficient critical state model, that can predict densification, pore water pressure buildup, liquefaction and cyclic mobility in sands. The numerical model can simulate successfully the generation, redistribution and dissipation of excess pore water pressures and reveal the deformational mechanisms leading to possible failure. The investigation will be performed in close collaboration with researchers from Shimizu Corporation, Japan and NTUA, Greece. This is an award supported under the 2nd year initiative, NSF 98-36 "US-Japan Urban Earthquake Disaster Mitigation Research."