不均匀波浪荷载作用下海积软黏土的动力特性

Dynamics characteristics of soft cohesive clay under non-uniform wave loading

为研究饱和海积黏土在均匀与不均匀波浪荷载作用下的循环特性,利用GDS空心圆柱扭剪仪进行了一系列不排水试验,在相同的初始固结状态下,对试样施加不同最大偏应力q_(max)、最小偏应力q_(min)的圆形及螺旋形应力路径的轴—扭联合循环载荷。分析了在考虑主应力轴旋转时,这两种不同应力路径的循环应力比R_(CS)与动应力比δ=q_(mim)/q_(max)对循环加载期间土体动力特性的影响。试验结果表明:R_(CS)与δ的增大均能提升黏土在波浪荷载下的孔压、轴向应变、双幅剪切应变及其速率,同时也能使土体轴向回弹模量与动剪切模量的衰减更严重,且δ的作用效果会随R_(CS)的增大而增大。当R_(CS)≤0.05时,土体在循环期间保持为“弹性安定或塑性安定”状态;而当R_(CS)≥0.06时,土体会处于“疲劳破坏”或“塑性蠕变”状态,其具体形式由R_(CS)与δ共同决定。土体在循环过程中的轴向回弹模量与动剪切模量近似呈一定比例。

In order to study the cyclic behavior of saturated marine clay under uniform and non-uniform wave loading,a series of undrained tests were conducted using the GDS hollow cylinder torsional shear apparatus.Under the same initial consolidation state,circular and helical stress paths with different maximum deviatoric stresses q_(max) and minimum deviatoric stresses q_(min) were applied to the specimens during axial-torsion combined cyclic loading.The influence of these two different stress paths on the cyclic stress ratio R_(CS) and cyclic pore pressure ratio δ=q_(min)/q_(max) on the dynamic properties of the soil during cyclic loading with consideration of the rotation of the principal stress axis was analyzed.The experimental results indicate that an increase in R_(CS) and δ both enhance the pore pressure,axial strain,shear strain,and their rates of increase in clay under wave loading,while also leading to more severe attenuation of the axial rebound modulus and dynamic shear modulus of the soil.The effect of δ increases with the increase of R_(CS).When R_(CS)≤0.05,the soil remains an“elastically stable or plastically stable”state during cycling.However,when R_(CS)≥0.06,the soil may be in a“fatigue failure”or“plastic creep”state,the specific form of which is jointly determined by R_(CS) and δ.The axial rebound modulus and dynamic shear modulus of the soil during the cycling process approximate a certain proportion.