纯主应力旋转条件下饱和黏土累积变形的热力学模型分析

不同于岩土弹塑性模型和经验回归模型,提供了一个基于颗粒固体流体动力学的热力学本构模型。该模型通过对岩土颗粒固体的弹性弛豫和颗粒熵运动等耗散机制的定量描述,可以模拟土体的非线性硬化、软化等宏观力学行为,尤其适用于主应力旋转土体累积塑性应变的模拟。纯主应力旋转条件下杭州黏土的模拟结果表明:即使不改变土体的主应力大小,纯主应力方向的旋转依然会引起土体的非弹性变形的积累。在主应力旋转过程中,土体的应变方向与应力方向并不一致,存在明显的非共轴现象。并且应变峰值的出现明显落后于应力峰值,应力–应变关系曲线存在较大的滞回圈,表明纯主应力旋转过程中也存在能量耗散,并非完全弹性过程。模型分析结果符合现有的试验结论。

Thermodynamic modeling of accumulated deformation of saturated clays under pure principal stress rotation

In contrast with elasto-plastic and empirically regressed models for soils, a novel thermodynamic constitutive model is proposed based on the granular solid hydrodynamics. Two energy dissipation mechanisms of elastic relaxation and granular entropy movement are mathematically described, which allows for the modeling of non-linear hardening and softening behaviors of soils and the modeling of accumulated plastic deformation due to the pure rotation of principal stresses in particular. The simulated results for Hangzhou clay indicate that the pure principal stress rotation can also cause inelastic deformation accumulation without any changes of principal stresses. During the rotation of principal stresses, the directions of principal strains do not coincide with the ones of the principal stresses, which is a typically non-coaxial behavior. The strain peaks fall behind the stress peaks. There exists a stress-strain hysteresis loop during the rotation of principal stresses, and the energy dissipation and non-elastic process should happen. All model results fairly fit the laboratory data.