Evaluation of Instability and Residual Deformation of Soft Cohesive Soils under Earthquake-induced Cyclic Lording

地震循环作用下软粘性土的失稳和残余变形评价

• 批准号: 07650562
• 负责人: YASUHARA Kazuya
• 金额: $ 1.41万
• 依托单位: Ibaraki University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07650562/
• 关键词: Earthquake,; Cohesive soil,; Cyclic loading,; River dyke,; Residual deformation,; Instability; 側方流動

Based on the results from laboratory investigation using cyclic and direct-simple shear tests on clays and their consideration into modeling for numerical analysis of behavior of embankments on soft ground, the following is pointed out :l) Degradation of stiffness and strength of cohesive soils triggered by undrained cyclic loading in triaxial conditions can be uniquely correlated to the magnitude of shear strain observed during cyclic loading. This is common with normally consolidated and overconsolidated specimens.2) Numerical analysis using a computer program for dynamic response analysis called SADAP incorporating the above-mentioned finding was carried out to obtain the design chart for predicting the earthquake-induced settlements as a parameter of the maximum acceleration and the overconsolidation ratio (OCR). A practical availability of the design chart was proved by comparing with the settlements observed in the results of centrifuge tests on the river dyke founded on soft clay.3) The results from numerical analysis were also given in the from of the design chart to forecast whether the dyke or the ground leads to instability during earthquakes.4) Through the results not only from the numerical analysis but also from the centrifuge tests, the effectiveness of preloading or surcharging was recognized as a countermeasure for increasing the stability of river dykes founded on soft clay.

基于室内循环和直剪试验的研究结果，并将其应用于软土地基上固结物特性的数值分析模型中，指出：（1）三轴不排水循环荷载作用下粘性土刚度和强度的退化与循环荷载作用下剪应变的大小有唯一的相关性; 2）利用SADAP动力响应分析程序进行数值分析，得到了以最大加速度和超固结比（OCR）为参数的地震沉降预测设计图表。通过与离心沉降试验结果的比较，证明了设计图的实用性; 3）在设计图中还给出了数值分析结果，以预测地震时堤坝或地基是否会发生失稳; 4）通过数值分析和离心试验结果，堆载预压或堆载的有效性被认为是提高软土地基上河堤稳定性的一种对策。

项目成果

Yasuhara,K., Murakami,S.et al.: "Cyclic softening and degradation of a plastic silt." Proc.Int.Symp.Defor.and Progressive Failure of Geomaterials. Vol.1. 617-622 (1997)

Yasuhara,K.、Murakami,S.et al.：“塑料淤泥的循环软化和降解。”

Yasuhara, K.&Nagano, M: "Post-cyclic behavior of clay in direct Shear tests" Proc.10th Asian Reg.Conf.SMFE. Vol.1. 119-122 (1995)

安原，K.

Yasuhara,K./Hyde,AFL: "Method for Estimating Postcyclic Undrained Secant Modulus of Clays" Jourual of Geotechnical & Geoenvironmental Eng.Proc.ASCE (米国土木学会論文誌). 123-3. 204-211 (1997)

Yasuhara, K./Hyde, AFL：“粘土循环后不排水割线模量的估计方法”《岩土工程与地质环境工程杂志》（美国土木工程师协会会刊）123-3 (1997)。

Yasuhara,K/N.Toyota: "Effects of Initial Static Shear Stress on Post-Cyclic Degradation of a plastic siet" Proc.14th ICSMFE (国際地盤工学会議). Vol.1(印刷中). (1997)

Yasuhara, K/N.Toyota：“初始静态剪切应力对塑料材料循环后降解的影响”Proc.14th ICSMFE（国际岩土工程会议）第 1 卷（出版中）。

Yasuhara, K.: "Earthqualce-Induced settlement in peafy ground" Proc. Intnil Workshop Eng. of Peat.Vol.1. 501-509 (1995)

Yasuhara, K.：“地球质量引起的豌豆地面沉降”Proc。