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CLC number: TU473

On-line Access: 2018-08-03

Received: 2017-08-30

Revision Accepted: 2018-01-25

Crosschecked: 2018-07-06

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Citations:  Bibtex RefMan EndNote GB/T7714

 ORCID:

Zhen Yan

https://orcid.org/0000-0003-1366-399X

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Journal of Zhejiang University SCIENCE A 2018 Vol.19 No.8 P.650-662

http://doi.org/10.1631/jzus.A1700461


A strength degradation model of saturated soft clay and its application in caisson breakwater


Author(s):  Zhen Yan, Yuan-zhan Wang, Zhong-xuan Yang, Zhong Xiao, Kun Pan

Affiliation(s):  Tianjin Research Institute for Water Transport Engineering, Ministry of Transport, Tianjin 300456, China; more

Corresponding email(s):   yanzhen19890206@163.com, zxyang@zju.edu.cn

Key Words:  Saturated soft clay, Undrained strength, Degradation model, Damage dependency, Numerical simulation


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Zhen Yan, Yuan-zhan Wang, Zhong-xuan Yang, Zhong Xiao, Kun Pan. A strength degradation model of saturated soft clay and its application in caisson breakwater[J]. Journal of Zhejiang University Science A, 2018, 19(8): 650-662.

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Abstract: 
In this paper we propose a degradation model to describe the damage-dependent behavior of saturated soft clay under cyclic loading, which is then applied to the analysis of a caisson breakwater. The degree of damage and remolding of soft clay is quantified by a damage parameter related to the accumulated plastic deviatoric strain. Through the correlation between the maximum pore pressure and the undrained strength of soft clay, we obtain a damage-dependent degradation model that employs the post-cyclic undrained strength degradation coefficient in terms of the cyclic stress ratio and the number of cycles. Based on the Tresca yield criterion, the degradation model of undrained strength of soft clay is numerically implemented in the user interface USDFLD of ABAQUS. The performance of this model is verified by a comparison between numerical results (finite element method) and experimental data (cyclic triaxial test). The model is applied to the numerical simulation of a caisson breakwater resting on a partially sand-filled soft clay seabed under cyclic wave loading. The cyclic stress distribution, pore pressure development, and strength degradation of the seabed soil are presented to illustrate the applicability and efficiency of the model in the analysis of the interaction between offshore structures and soft ground.

This manuscript presents a strength-degradation model for soft clay under cyclic loading. This mode assumes a strength degradation form and obtains the parameters by fitting curves. The post-cyclic strength is then implemented into Tresca model, which is further employed to analyze the post-cyclic behaviors of caisson breakwater.

饱和软黏土不排水强度弱化模型及其在沉箱式防波堤的应用分析

目的:本文旨在建立简单实用的饱和软黏土不排水强度损伤弱化模型,应用于波浪循环荷载作用下沉箱式防波堤与软土地基相互作用的非线性数值计算,为解决防波堤软土强度弱化计算问题提供有效途径.
创新点:1. 基于不排水强度循环损伤弱化机理,得到软黏土不排水强度随循环荷载作用次数和应力水平的变化规律; 2. 结合Tresca屈服准则进行数值开发,应用于波浪循环荷载作用下沉箱式防波堤与软土地基相互作用的数值计算.
方法:1. 引入累积塑性变形相关的损伤变量表征土体结构性的损伤和重塑对软黏土不排水强度弱化的影响(公式(3)和(11)); 2. 建立软黏土不排水强度随循环荷载作用次数和应力水平变化的损伤弱化模型(公式(14)); 3. 结合Tresca屈服准则,实现软黏土不排水强度损伤弱化的数值计算过程(图9); 4. 针对烟台软黏土动三轴试验数据进行分析,对模型及其数值开发过程进行验证(图11和12); 5. 将模型应用到软土地基上沉箱式防波堤数值运算,分析软土地基响应,验证模型的有效性(图15~18).
结论:1. 在临界循环应力比以下,损伤变量和归一化最大孔压比随循环荷载作用次数的增加逐渐增大,并趋于稳定;随循环应力比增大逐渐增大.循环后不排水强度折减系数随着循环荷载作用次数和循环应力比的增加而减小. 2. 有限元数值开发过程是正确的,不排水强度损伤弱化模型是合理的. 3. 该模型简单实用,可应用于波浪等循环荷载作用下沉箱式防波堤与软土地基相互作用的非线性数值计算,且能模拟循环荷载下软土地基的孔隙水压力增长以及不排水强度弱化等响应. 软土地基的响应主要分布在基床两趾及正下方的软土层上部.

关键词:饱和软黏土;不排水强度;循环弱化模型;损伤;数值模拟

Darkslateblue:Affiliate; Royal Blue:Author; Turquoise:Article

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