波浪荷载作用下软黏土软化模型研究

Research on Softening Model of Soft Clay under Wave Load

波浪荷载能引起海床土体的主应力轴连续旋转。不同于地震、交通等循环荷载,在周期性波浪荷载作用的土体应力路径方式下,软黏土的软化效用更为明显。本文分别对天然和扰动的海床土体在波浪荷载作用下的应力响应进行模拟,并分析应力路径的特点;为描述软化后的应力-应变关系,将软化效用和累积塑性应变的参数引入到能够反应土体动力非线性的Hardin-Drnevich模型中,建立修正模型,使之能够反应软黏土体软化与塑性应变累计特性;通过与模拟波浪荷载下土体应力特征的循环耦合试验结果进行对比分析,验证该修正模型的可靠性。

Wave load causes continuous rotation of the principal stress axes of seabed soil.Unlike seismic load and traffic load,under the action of cyclical wave load,stiffness softening of soft clay is much more obvious.Numerical simulation is applied to obtain the stress response of undisturbed and disturbed seabed soil,and to analyze the characteristics of the stress path.Under wave loads,the main feature of the seabed soil is the continuous rotation of its maximum principal stress axis;the maximum principal stress＇ cycle is similar to the wave load cycles.Under the influence of the structure in the seabed disturbance,the soil＇s stress path changed under the wave load,and the factors that affect the stress path can be generalized using the initial principal stress orientation,the initial stress ratio,the angle of the major principal stress direction,and other factors.To describe the relation of a soil＇s stress and strain after stiffness softening,two parameters were introduced to the Haridin-Drnevich model to reflect the stiffness softening and cumulative plastic strain phenomenon,and these two parameters are a function of the soil＇s initial status,which influences its stress path under wave load.The cyclic coupling shear tests can probably simulate the wave load and therefore,this modified Haridin-Drnevich model should be compared with the results of cyclic coupling shear tests where wave loads can be applied to verify its reliability.