考虑温度影响的冻土蠕变本构模型

A creep constitutive model for frozen soils considering the influence of temperature

冰作为冻土的基本组成部分,对冻土蠕变的加速蠕变阶段有重要影响。温度通过影响冻土中冰的冻结与融化过程,及其黏塑性流动,引起冻土结构的强化与弱化,从而成为了决定冻土蠕变力学行为的关键因素之一。同时,外部应力也造成冻土的强化与弱化,影响着冻土的蠕变。通过引入硬化因子与损伤因子来考虑温度、应力造成的冻土材料强化与弱化。硬化因子H代表了蠕变过程中强化效应的大小,而损伤因子D则代表了由弱化效应造成的冻土材料相关参数的折减比例,进而提出了适用于冻土的改进西原蠕变本构模型。该模型预测值与试验数据的比较表明:改进的模型不仅能较好地描述初始蠕变阶段、稳定蠕变阶段,而且相比于传统模型,能更好地描述冻土加速蠕变阶段,具有合理性与一定的实用性。

As a basic portion of frozen soils, ice has a significant impact on the accelerated creep stage of frozen soils. Temperature gives rise to hardening and weakening of frozen soil structure by affecting the freeze-thaw process of ice in frozen soils, as well as its viscoplasticity flow, thus becoming one of the key factors to determine the behavior of frozen soils. Meanwhile, the external stress also causes hardening and weakening, affecting the creep of frozen soils. Both hardening variable and damage variable are introduced here to consider hardening and weakening of the frozen soils resulted from variation of temperature and stress. Among them, the hardening factor H represents the magnitude of hardening effect in the process of creep, while damage factor D represents the reduction ratio of related parameters of frozen soils caused by the weakening effect, and then an improved Nishihara model is developed, the expression of improved Nishihara model under complicated stress state is derived as well. The comparisons between model predictions and available experimental results show that the improved model can not only describe the initial creep stage and the stable creep stage well, but also agrees well with the strain law growing exponentially with time in the accelerated creep stage, which demonstrates its accuracy and usefulness.