Investigation on freeze-thaw damage mechanism of porous rock with discrete element method
The study of the degradation mechanism of freeze-thaw damaged rock holds significant theoretical importance in understanding freeze-thaw disasters,predicting disasters,and designing tunnel protection systems in cold regions.Based on the volume expansion theory,this research establishes a correlation between irreversible volume increase and the number of freeze-thaw cycles,and also deduces the law of radial heat transfer for cylindrical samples during freeze-thaw cycles.Considering the freeze-thaw damage process of saturated samples,a model of rock freeze-thaw damage based on discrete elements is developed.The physical and mechanical properties of sandstone with different freeze-thaw cycles are tested to validate the model,using stress-strain curves and uniaxial compressive strength.Building upon this,the growth and distribution of cracks in rock samples during freeze-thaw cycles are analyzed,and the crack growth process under coupled freeze-thaw-stress conditions is studied.The research findings indicate that as the number of freeze-thaw cycles increases,the development of cracks undergoes three stages:slow,fast,and then steady.The number of cracks increases radially from the inside to the outside of the sample.Approximately 80％of the frost heave cracks are distributed in the circular column area 10-25 mm away from the sample's axis.When the number of freeze-thaw cycles is less than 80,the increase in the number of cracks follows an exponential function relationship.However,when the number of freeze-thaw cycles exceeds 80,the number of cracks increase logarithmically with their distance from the center of the circle.During the freeze-thaw cycle,the damage in the sample primarily occurs through tensile failure,and the freeze-thaw damage process of the rock is influenced by the initial pore structure.
freeze-thaw damagediscrete element methodvolume expansionheat conductioncracks
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