Effects of soil heterogeneity on pile foundations under seismic loads

地震荷载作用下土体非均质性对桩基的影响

• 批准号: 203795-2006
• 负责人: Popescu, Radu
• 金额: $ 1.54万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2006
• 资助国家: 加拿大
• 起止时间: 2006-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=332143
• 关键词: Effects; soil; heterogeneity; pile; foundations

Seismic induced liquefaction of saturated soil is still a major cause of earthquake damage to deep foundations, in spite of relatively large safety margins used in design. This proposal outlines a combined experimental and numerical study aimed at addressing a series of questions regarding failure mechanisms and interaction forces for piles in liquefying soil that have not been answered yet, and at providing the industry with a reliable tool and guidelines for seismic design of deep foundations. It is well understood today that soil properties vary from one point to another even within geologically distinct layers. The effects of this natural soil heterogeneity on soil liquefaction and soil pile interaction will also be addressed. In this respect, recent theoretical research identified a very interesting behaviour of such natural soils subjected to seismic loads that is likely to have significant influence on design practices in earthquake geotechnical engineering. To date, there is no experimental verification available to the practicing engineering community to help in recognizing, quantifying and accepting the above-mentioned behavior of heterogeneous soils.   A series of original centrifuge experiments for seismic analysis of pile foundations in randomly heterogeneous soil are proposed in this research program to investigate the atypical soil behaviour identified in theoretical studies and to quantify its effects on deep foundations. A state-of-the-art finite element code for dynamic effective stress analysis of soil-structure systems will be calibrated based on the experimental results and used to expand the scope of the experimental program. Both experimental and numerical results will then be used to develop, calibrate and validate a computationally effective tool for seismic analysis of pile foundations, readily available for current design applications. Finally, the new tool will be used in a systematic numerical study to provide design guidelines for a wide range of field situations and seismic loads. The soil materials for experiments and the examples for theoretical developments will be selected from the Fraser River Delta in British Columbia, a densely populated region highly vulnerable to earthquake hazards and soil liquefaction.

饱和土地震液化是引起深基础地震破坏的主要原因之一，尽管设计中采用了较大的安全裕度。该提案概述了一个综合的实验和数值研究，旨在解决一系列问题，关于桩的破坏机制和相互作用的力量，在桩土中，还没有得到回答，并提供了一个可靠的工具和指导方针，深基础的抗震设计的行业。今天，人们已经很好地理解，即使在地质上不同的地层中，土壤的性质也会从一个点到另一个点发生变化。这种天然土壤的异质性对土壤液化和土桩相互作用的影响也将得到解决。在这方面，最近的理论研究确定了一个非常有趣的行为，这样的天然土壤受到地震荷载，可能有显着的影响，在地震岩土工程的设计实践。到目前为止，还没有实验验证提供给实践工程界，以帮助认识，量化和接受上述行为的非均质土壤。 在这项研究计划中，提出了一系列的原始离心试验随机非均质土中的桩基地震分析，以调查在理论研究中确定的非典型土壤行为，并量化其对深基础的影响。一个国家的最先进的有限元代码的动态有效应力分析的土壤结构系统将校准的基础上的实验结果，并用于扩大范围的实验程序。实验和数值计算结果将被用来开发，校准和验证一个计算有效的工具，用于桩基地震分析，随时可用于当前的设计应用。最后，新工具将用于系统的数值研究，为各种现场情况和地震荷载提供设计指南。用于实验的土壤材料和用于理论发展的示例将选自不列颠哥伦比亚省的弗雷泽河三角洲，该地区人口稠密，极易受到地震灾害和土壤液化的影响。