一个能够模拟软土时效特性的简单弹黏塑性模型(英文)

基于Perzyna超应力理论与修正剑桥模型,建立了一个能够模拟软土时效特性的简单的弹黏塑性本构模型,提出了参数的实验室确定方法。以室内试验为基础,模拟了不同试验条件下软土的时效特性:应变速率对先期固结压力和不排水抗剪强度的影响;一维固结与次固结特征及竖向应力对次固结系数的影响;不同应力水平下的不排水蠕变特征;不同应变水平下的应力松弛特征。通过实验数据与数值模拟的比较,对模型进行了验证,发现上述本构模型能够较好地描述不同加载路径下的正常固结与微超固结土的时效特征。同时,通过对同一试样的多阶段加卸载三轴实验、现场压力仪实验及实验室压力仪实验的模拟,发现此模型可以较好地拟合实验过程中复杂应力路径下软土的时效特征。

Modelling of time-dependent behaviour of soft soils using simple elasto-viscoplastic model

The purpose of this study was to present the development of an elasto-viscoplastic constitutive model to describe the time-dependent behaviour of soft soils. The elasto-viscoplastic model was established within the framework of Perzyna's overstress theory and the Modified Cam Clay model. The stress-strain relationship was solved by using an implicit backward Euler method of stress with updated algorithm, and implemented in a finite element program. Different types of tests were simulated using the EVP-MCC model to simulate the time-dependent behaviour of soft soils under different loading conditions, such as the strain rate effects on preconsolidation pressure as well as on undrained shear strength; the primary, secondary consolidation behaviour and stress effects on secondary compression coefficient ; the creep and stress relaxation features under different stress levels. It was shown that the model could satisfactorily describe the time-dependent behaviour of normally consolidated or slightly overconsolidated clayey soils along different loading paths. Time-dependent properties behaved in multiple stages triaxial tests, and field and laboratory pressuremeter tests had also been successfully simualted by the proposed EVP-MCC model.