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Strength Decreasing due to Dynamic Stress of Earthquake

地震动应力导致强度下降

基本信息

批准号：
04650442
负责人：
YAGI Norio
金额：
$ 1.34万
依托单位：
Ehime University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650442/
关键词：
Sand Clayy soil Cyclic shear Liquefaction Pore water pressure Shear strength Simple shear apparatus 非排水せん断強度応力履歴

项目摘要

This research consists of three parts, that is, 1) pore water pressure and liquefaction of saturated sands due earthquake, 2) strength characteristics of clayy soil to which a cyclic shear stress have applied, 3) development of a simple shear apparatus in which arbitrary stress conditions can be controlled. The cyclic shear tests for the three kinds of soils were carried out using the triaxial apparatus. Amplitudes of strain of both compression and extesion sides become nearly same by the proposed method of giving cyclic shear stress. Resistance of silty soil of OCR=5 for liquefaction corresponds to one of sand of 40% relative density. An increase of pore water pressure in one cycle of shear stress can be expressed as the function of the ratio of the amplitude of the shear stress to the effective stress and it is possible to calculate the pore water pressure due to a random shear stress wave. The resistance for liquefaction have good correlation to a dilatancy coefficient. The pore water pressure of a clayy soil due to cyclic shear is also expressed by the same function for sand. The strength parameters in terms of effective stress is constant regardless of disturbance and history of cyclic shear, but the effective stress path is influenced by the history of cyclic shear. The coefficient of pore water pressure at failure and the effective stress path are determined by the proposed parameter b for the soil having the history of cyclic shear. Magnitude of shear strength of the specimens which have same water content is in order of over consolidated, having cyclic shear and remolded reconsolidation. The strength parameters from the simple shear apparatus is nearly same one from the triaxial test.

本研究包括三个部分：1）饱和砂土的孔隙水压力与地震液化; 2）循环剪应力作用下粘性土的强度特性; 3）可控制任意应力条件的简易剪切仪的研制。利用三轴仪对三种土进行了循环剪切试验。通过循环剪应力的给定，使压侧和伸侧的应变幅值趋于一致。OCR=5的粉质土的抗液化性相当于相对密度为40%的砂土的抗液化性。在一个剪应力循环中孔隙水压力的增加可以表示为剪应力幅值与有效应力之比的函数，并且可以计算由于随机剪应力波引起的孔隙水压力。抗液化强度与液化系数有较好的相关性。粘性土的循环剪切孔隙水压力也可以用同样的函数来表示。以有效应力表示的强度参数不受扰动和循环剪切历史的影响，但有效应力路径受循环剪切历史的影响。对于具有循环剪切历史的土壤，破坏时的孔隙水压力系数和有效应力路径由建议的参数B确定。相同含水量的试样抗剪强度大小顺序为超固结、循环剪切和重塑再固结。单剪仪测得的强度参数与三轴试验测得的强度参数基本一致。