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Evaluation of strength and deformation characteristics of sandy gravels based on in situ freezing method

基于原位冻结法的砂砾石强度及变形特性评价

基本信息

批准号：
63302051
负责人：
TOKIMATSU Kohji
金额：
$ 2.11万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Co-operative Research (A)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63302051/
关键词：
Dynamic property Freezing sampling In situ test Laboratory test Liquefaction resistance Penetration test Sandy gravel Shear wave velocity

项目摘要

High-quality undisturbed samples of sandy gravel were obtained by in situ freezing methods from an alluvium deposit. The standard penetration test, the large diameter penetration test, and the seismic downhole test were made at the same site. The purpose of the investigation is to study the static and dynamic properties of undisturbed gravely soils in the laboratory, and to investigate their correlations with the index properties obtained from the in situ tests.Drained static tests and undrained cyclic tests were conducted on the samples to determine the static strength, the liquefaction resistance and the correlation of shear modulus and damping factors with shear strain. The test results together with those of previous studies have shown that the penetration resistances become less correlated with dynamic strength as the grain size increases, and that such trend is more significant for the SPT than for the LPT. The tendency indicated that correction should be made to measured penetration resistances to allow for the effect of the presence of large particles. Based on the finding, tentative correction factors are presented in terms of the mean grain size, and the correlation of dynamic strength was reevaluated with these values.. The corrected penetration resistances show good agreement with the dynamic properties, indicating the effectiveness of the proposed method of correction.The test results also indicated that there is a well-defined correlation between liquefaction resistance and shear modulus normalized with respect to minimum void ratio and confining pressure. Based on the finding, a simplified method is presented for estimating liquefaction resistance from shear wave velocity.

采用原位冻结法从某冲积层中获得了高质量的原状砂砾样。在同一场地进行了标准侵彻试验、大直径侵彻试验和地震井下试验。研究的目的是在实验室中研究未受扰动的严重土壤的静态和动态特性，并探讨它们与原位试验中获得的指标特性的相关性。对试样进行排水静力试验和不排水循环试验，确定试样的静力强度、抗液化能力以及剪切模量和阻尼系数与剪切应变的相关性。试验结果与前人的研究结果表明，随着晶粒尺寸的增大，侵彻阻力与动强度的相关性降低，且这种趋势在SPT中比LPT中更为显著。这种趋势表明，应该对测量的渗透阻力进行修正，以考虑到大颗粒存在的影响。在此基础上，提出了以平均粒径为单位的初步修正系数，并利用这些修正系数重新评价了动强度的相关性。修正后的侵彻阻力与动态特性吻合较好，表明修正方法的有效性。试验结果还表明，液化阻力与按最小空隙比和围压归一化的剪切模量之间存在明确的相关关系。在此基础上，提出了用横波速度估算液化阻力的简化方法。