Dynamic characteristics and damage model of freezing thawing red sandstone under impact load

YU Yang; JIANG Qincai; WANG Zehua; LU Yuyin; GUO Qixiang; ZENG Huiming

doi:10.13225/j.cnki.jccs.2024.0641

Abstract：To study the dynamic mechanical properties and damage evolution characteristics of freeze-thaw rocks under impact loads,0,15,30,45,and 60 freeze-thaw cycle tests and dynamic impact tests were conducted on red sandstone in cold regions.The effects of strain rate and freeze-thaw damage on the dynamic mechanical properties of red sandstone were analyzed.Based on the damage evolution equation considering the damage threshold,a damage viscoplastic dynam-ic constitutive model of freeze-thaw red sandstone was constructed based on the combination element model theory and statistical damage theory,and the rationality and applicability of the model were verified.The results show that red sand-stone exhibits freeze-thaw cycle effects and strain rate effects,and its dynamic peak strength decreases with the increase of strain rate or the decrease of freeze-thaw cycle times.The higher the strain rate,the stronger the sensitivity to freeze-thaw damage;the introduction of dynamic peak strength loss γ can eliminate the strain rate effect under impact loads and more intuitively reflect the impact of freeze-thaw cycles on the dynamic peak strength of rocks under different impact loads.The damage threshold point is 45 freeze-thaw cycles,and after 45 cycles,the freeze-thaw damage tends to stabilize;compared with unfrozen and thawed environments,a larger scale crack network is formed internally,and the failure mode changes from splitting to shear failure.The mechanical properties deteriorate significantly in the freeze-thaw environment;the lin-ear elastic stage of sandstone exhibits obvious behavior after freeze-thaw cycles.Based on the D-P failure criterion,a dam-age evolution equation considering the damage threshold is derived,which is more reasonable.Based on the Zhu-Wang-Tang constitutive model,a viscoelastic plastic dynamic constitutive equation for constructing damaged bodies is intro-duced,reflecting the comprehensiveness of the constitutive model;the dynamic constitutive model established in this art-icle well reflects the complex characteristics of damage softening,viscoelasticity,and viscoplasticity exhibited by red sandstone during load deformation,and also reflects the influence of freeze-thaw damage on the dynamic mechanical properties of red sandstone;the conclusions obtained can provide reference for studying the dynamic impact failure of rocks in seasonal high-altitude and cold regions.