Investigating Influence of Freeze-Thaw Cycles on the Degradation of Sandstone Through Discrete Method Modeling

Abstract

ABSTRACT: In this study, the discrete element modeling (DEM) method is adopted to evaluate the influence of freeze-thaw cycles (FTC) action on the mechanical properties of sandstone. A water-rich rock model is built, with rock and water compositions represented by particles of different sizes. To overcome the intrinsic porosity limitation of DEM model and better represent the saturated rock sample, we develop an algorithm to include particles of smaller and varying sizes into rock pores. The ice-water phase change and the resulting accumulation of residual strain are considered by developing a modified elastoplastic model. The rationality of this model is first validated by comparing numerical results with published experimental data. Numerical results highlight the FTC deterioration of the uniaxial compressive strength and Young’s modulus of rock specimens. We establish exponential correlations between the freeze-thaw cycle number and the rock’s mechanical properties such as the uniaxial compressive strength, Young’s modulus and strain energy, showing consistent trends with experimental observations. Inter-particle contact damage also reflects the formation and distribution of micro-fractures in rock specimens under freeze-thaw cyclic treatments. This study provides new insights into the rock degradation process under changing climate and could contribute to the future design and assessment of climate-resilient infrastructure. 1. INTRODUCTION Rock is a typical porous material that allows water to enter pores and micropores by capillary action in a water-rich environment (Amirkiyaei et al., 2021). When the temperature is below 0 °C, the water in pores is frozen as ice whose volume increases by about 9% (Hou et al., 2021). During the phase change of water, the frost heaving pressure increases due to the constrain of surrounding rock (Wang and Zhou, 2018). The frost heaving pressure produces additional microcracks or enlarges the pre-existing discontinuities of rock, allowing more water to fill into rock after ice thawing and producing more damage under the subsequent freezing. As a result, the physical and mechanical properties of rock are deteriorated after increasing freeze-thaw cycles. Therefore, understanding and predicting rock behaviors after freeze-thaw cycles are critical to prevent the damage of rock-based infrastructures in cold regions and regions that undergo seasonal weather changes.