VALUATION OF EARTH PRESSURES ACTING ON FOUNDATIONS DURING STRONG

强震期间作用于地基的土压力的评估

基本信息

批准号：
11450203
负责人：
TOKIMATSU Kohji
金额：
$ 7.36万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

The field performance of buildings during recent catastrophic earthquakes is summarized, with emphasis placed on the effects of ground failure, nonlinear site response, and dynamic and permanent ground displacement. In addition to in-situ lateral load on steel pipe piles, large-scale shaking table tests are conducted to study the effects of soil-pile-structure interaction including those of nonliquefied crust overlying liquefied soil and p-y behavior of piles on pile performance. It is shown that : (1) the p-y behavior is affected by such factors as the pore pressure ratio, relative displacement of soil and pile, and soil density ; and (2) the total earth pressure acting on embedded foundation is induced mainly by the relative displacement between soil and foundation. Back-analysis is conducted for well-documented case histories of pile foundations to estimate the scaling factors for p-y springs of laterally spreading soils. The analytical results show that both the coefficient of the horizontal subgrade reaction of piles and the maximum reaction force of laterally-spreading soils are 0.05-0.2 times those of non-liquefied soils, consistent with the shaking table test results. Both effective stress and simple p-y analyzes, which incorporate the above findings, are conducted for several buildings that suffered various patterns of damage during soil liquefaction in the 1995 Hyogoken-Nambu earthquake. A comparison of the computed results with the filed observation indicates that both analyzes are cap able of discriminating damaged from undamaged foundations as well as of estimating the damage portion and severity with a reasonable degree of reliability.

总结了最近发生的灾难性地震中建筑物的现场性能，重点是地面破坏、非线性场地响应以及动态和永久地面位移的影响。除了钢管桩的原位侧向荷载之外，还进行了大型振动台试验，以研究土-桩-结构相互作用的影响，包括液化土上覆盖的非液化结皮和桩的 p-y 行为对桩性能的影响。结果表明：（1）p-y行为受孔压比、土体与桩体相对位移、土体密度等因素的影响； (2)作用在预埋地基上的总土压力主要是由土体与地基之间的相对位移引起的。对有据可查的桩基案例进行反分析，以估计横向扩展土壤的 p-y 弹簧的比例因子。分析结果表明，桩的水平路基反力系数和侧展土的最大反力均为非液化土的0.05～0.2倍，与振动台试验结果一致。对 1995 年兵库县南部地震中土壤液化过程中遭受各种损坏的几座建筑物进行了有效应力和简单 p-y 分析，其中纳入了上述研究结果。计算结果与现场观察的比较表明，两种分析都能够区分损坏的基础和未损坏的基础，并能够以合理的可靠性程度估计损坏部分和严重程度。