01628164

Component

More than 50 percent of the exposed land surface in the Northern Hemisphere undergoes seasonal freezing and thawing processes. The processes involve heat and moisture exchange between atmosphere and land surface as well as thermal and hydraulic flows inside the unsaturated soil layers in the vadose zone. Internal stress is generated and dissipated during the freezing and thawing cycles, leading to the volume expansion and contraction of soils, which causes pavement cracking, foundational settlement, and other serious damages to the civil infrastructure. In this paper, a microstructure-based model is developed to describe frozen soil in four phases based on the volumetric content of each phase. The model is converted into a finite element model. The thermal, hydraulic, and mechanical properties of each soil phase (soil particle, ice, water, and air) are applied based on the microscopic structures. The matric suction associated with liquid water content, thermal and mechanical processes associated with phase change during freezing/thawing are described holistically. Coupled thermo-hydro-mechanical model is implemented based on the microstructure represented four phase model, which combines the advantages of discrete element model in simulating the mechanical behaviors and the computational efficiency of finite element model. The simulation results show that the coupled model holistically describes the thermal and hydraulic flows during the freeze-thaw cycle. These include the temperature driven change of matric suction. Besides, with the use of model for individual phase, the generation of internal stresses due to freezing/thawing processes can be determined, which is an common underlying mechanism for freezing/thaw damages. Overall, this study offers a new modelling approach to holistically analyze the thermal, hydraulic, and mechanical behaviors of unsaturated frozen soils.

This paper was sponsored by TRB committee AFP50 Standing Committee on Seasonal Climatic Effects on Transportation Infrastructure.

01618707

17-05648

English

16p

2017

Transportation Research Board 96th Annual Meeting

Digital/other

Figures; Maps; References; Tables

Finite element method; Frozen soils; Hydraulic properties; Mechanical properties; Microstructure; Simulation; Thaw; Thermal properties; Unsaturated soils

Geotechnology; Transportation (General)

Transportation Research Board Annual Meeting 2017 Paper #17-05648

TRIS, TRB, ATRI

Dec 8 2016 12:15PM