海相沉积软黏土的弹塑性本构模型研究

在深入探讨海相沉积原状软黏土压缩、变形等力学特性和详细分析加载屈服面随荷载情况变化的基础上,确认了海相沉积原状软黏土的强度、变形特性与结构屈服应力密切相关。即当固结压力小于结构屈服应力时,其力学特性与超固结重塑土的力学特性类似;当固结压力大于结构屈服应力时,其力学特性与正常固结重塑土的力学特性类似。为描述海相沉积原状软黏土的上述力学特性,将姚仰平等提出的超固结重塑土本构模型引入到海相沉积软黏土弹塑性本构模型的构建中。在本构模型构建过程中,考虑了海相沉积原状软黏土具有的抗拉强度及其演化规律,软黏土强度包线的特点及其进一步修正的表达式,使模型更符合海相原状软黏土的强度、变形特性。最后,将3种不同海相沉积软黏土固结排水剪切试验得到的应力-应变-体变曲线与模型预测结果进行对比。比较结果显示,本文提出的弹塑性本构模型能很好地描述海相沉积原状软黏土的剪缩硬化、剪胀软化以及变形的应力水平依存性等力学特性。

An elastoplastic constitutive model for marine sedimentary soft clays

On the basis of the discussion on mechanical behavior and the detail analysis of the change of yield surface with loading on natural marine soft clay, the effects of structural yield stress on the deformation and strength characteristics of marine soft clays, are confirmed, i.e. the behavior is similar to that of overconsolidated remolded clay when the confining pressure is lower than the structure yield stress while the behavior is similar to that of normally consolidated remolded clay when the confining pressure is larger than the structure yield stress. To much better describe the above mechanical behaviors of marine soft clay, the overconsolidated remolded model proposed by Yao et al. is introduced to establish the elastoplastic constitutive model for marine soft clays. Moreover, the tensile strength existing in marine soft clay and its evolution law are also taken into consideration. The equation of strength envelope of marine deposit soft clay is further revised in the constitutive model to reflect the strength and deformation characteristics of this marine soft clay. Finally, the comparison of stress-strain-volume strain curves between the measured and predicted results shows that the elastoplastic constitutive model can describe well the mechanical behavior of the strain-hardening/softening and dilatancy characteristics; and the deformation characteristics are dependent on the confining pressure of marine soft clay.