摘要
文章针对天津滨海K0固结饱和软黏土,开展轴向及侧向耦合循环加载真三轴试验。重点探讨了循环中主应力系数及循环应力水平对软黏土动应力应变响应的影响。试验结果表明:同一循环应力水平,循环中主应力系数越大,累积永久大主应变越小,中主应力的增大对大主应变的发展有抑制作用;循环中主应力系数在0.4~0.6,存在某一临界值,其为中主应变发生正负反向的临界点。同一中主应力系数,循环应力水平越高,土样最终累积永久主应变越大;循环应力水平在0.4~0.46,存在某一临界值,其为土样循环振稳及失稳的临界点。在大主应力方向,循环中主应力系数越小,土体刚度弱化越显著;在中主应力方向,刚度弱化程度随中主应力系数的变化并非单调。循环应力水平越大,土体刚度弱化越显著。利用广义剪应变表征三维复杂应力状态下土单元的应变水平,建议了能够预测任意给定循环中主应力系数、循环应力水平及循环次数下累积永久广义剪应变的指数函数表达式。研究成果以期为波浪、交通等复杂动荷载作用下软黏土地基的稳定性分析及变形计算提供试验依据。
The true triaxial tests under axially and laterally coupled cyclic loading were carried out for K0-consolidated saturated soft clay from Tianjin Binhai.The effects of cyclic intermediate principal stress coefficient and cyclic stress level on the dynamic stress-strain response of soft clay were discussed.The test results show that for the same cyclic stress level,the larger the cyclic intermediate principal stress coefficient is,the smaller the cumulative permanent major principal strain is,and in addition the increase of intermediate principal stress can inhibit the development of major principal strain.There is a critical value in the range from 0.4 to 0.6 for the intermediate principal stress coefficient,which is the critical point of intermediate principal strain transiting from the positive to the negative.For the same intermediate principal stress coefficient,the permanent cumulative principal strain of soil sample increases with the cyclic stress level.There is a critical value of the cyclic stress level in the range from 0.4 to 0.46,which is the critical point of cyclic shakedown and instability of soil samples.In the direction of major principal stress,the degradation of soil stiffness becomes more significant with the decrease of cyclic intermediate principal stress coefficient.In the direction of intermediate principal stress,the stiffness degradation degree may not vary monotonically with intermediate principal stress coefficient.The degradation of soil stiffness becomes more evident with the increase of the cyclic stress level.The generalized shear strain was used to characterize the strain level of soil element under three-dimensional complex stress state,and an exponential function expression for cumulative permanent generalized shear strain under any given cyclic principal stress coefficient,cyclic load level and cycle numbers was proposed.The research results can provideexperimental basis for stability analysis and deformation calculation of soft ground under complex dynamic loads such as waves and traffic loads.
作者
卢力强
程星磊
刘举
孙晓涵
Lu Liqiang;Cheng Xinglei;Liu Ju;Sun Xiaohan(Key Laboratory of Soft Soil Engineering Character and Engineering Environment of Tianjin,Tianjin Chengjian University,Tianjin 300384,China;College of Civil Engineering,Tianjin Chengjian University,Tianjin 300384,China)
出处
《土木工程学报》
EI
CSCD
北大核心
2023年第2期100-109,共10页
China Civil Engineering Journal
基金
天津市教委科研计划项目(2018KJ165)。
关键词
K0固结
软黏土
循环加载
真三轴试验
中主应力
K0-consolidated
soft clays
cyclic loading
true triaxial tests
intermediate principal stress
