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: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=364202
• 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.

尽管在设计中使用了相对较大的安全裕度，但地震引起的饱和土壤液化仍然是深层基础地震损坏的主要原因。该提案概述了一项联合实验和数值研究，旨在解决有关失效机制和相互作用的一系列问题。液化土壤中桩的受力问题尚未得到解答，并为行业提供了深基础抗震设计的可靠工具和指南。今天，人们充分了解，即使在不同的地质条件下，土壤特性也会因地点而异。这种自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，最近的理论研究发现了这种自然土壤在地震荷载作用下的一个非常有趣的行为，这可能对设计产生重大影响。迄今为止，工程实践界还没有可用的实验验证来帮助识别、量化和接受异质土壤的上述行为。本研究计划提出了对随机异质土壤中的桩基进行地震分析，以研究理论研究中发现的非典型土壤行为，并量化其对深层基础的影响，用于动态有效应力分析的最先进的有限元代码。土-结构系统的计算将根据实验结果进行校准，并用于扩大实验程序的范围，然后使用实验和数值结果来开发、校准和验证桩基础抗震分析的计算有效工具。随时可用最后，新工具将用于系统的数值研究，为各种现场情况和地震载荷提供设计指南，用于实验的土壤材料和理论发展的示例将从弗雷泽中选择。不列颠哥伦比亚省的河流三角洲是一个人口稠密的地区，极易遭受地震灾害和土壤液化。