Thermal-Hydro-Mechanical Model for Freezing and Thawing of Soils.

摘要

Frost susceptible soils are vulnerable to frost action in seasonal freezing and permafrost regions, such soils may experience large deformations upon temperature changes. Frost heave and soil strengthening occurs as the soils freeze, whereas settlement and thaw weakening is expected during the melting process. Consequently, significant damage to infrastructure in cold regions can be caused by freezing-thawing cycles. Accounting for soil behavior during freezing and thawing is essential for engineering design and minimizing frost-related damage. An elastic-plastic constitutive model for freezing and thawing soils is developed. The constitutive relationship is temperature-dependent, capable of capturing the deformation behavior and strength evolution of the soil subjected to arbitrary loading and thermal boundary conditions. The yielding of the frozen soil is based on hardening plasticity and a critical state framework, with the pore ice content and specific volume as two parameters responsible for hardening and softening of the soil. A modified porosity rate function is adopted to simulate formation of ice lenses in freezing frost-susceptible soils. The function is implemented into a finite element system with a thermal-hydro-mechanical framework used to capture the multi-physics processes of soil freezing and thawing. The system is calibrated using available frost heave laboratory test data. It can be used as a tool to solve complex boundary value problems related to engineering practice. Results of the simulations are encouraging, and they indicate a very realistic response of the model to changing thermal boundary conditions.