冻融循环下砂岩的动态劈裂特性与应变演变机理OA北大核心CSTPCD

This study attempts to investigate the dynamic tensile mechanical properties of sandstone un-der freeze-thaw cycle by using the split Hopkinson pressure bar(SHPB)test system to perform dynamic splitting tests on sandstone samples with freeze-thaw cycle 0,10,20 and 40 times at different impact speeds.Also adopting the high-speed digital image correlation(DIC),we observed the dynamic tensile failure process of the specimen,where we analyzed the strength characteristics,deformation process and failure form of frozen sandstone under dynamic tensile stress in different freeze-thaw cycles.Results show that 1)the dynamic tensile σ-t curves of frozen sandstone and ordinary sandstone exhibit similar patterns of stress variation under different freeze-thaw cycles,which can be divided into four stages:low speed growth section,high speed growth section,peak plateau section and decreasing section;2)the peak tensile stress increases linearly with the increase of stress loading rate;3)the peak tensile stress of frozen rock has a certain freeze-thaw cycle effect,and there is a strong correlation between the peak ten-sile stress and the number of freeze-thaw cycles.The dynamic tensile strength of frozen rock increases first and then decreases as the number of freeze-thaw cycles increases.Under the same impact pressure,the frozen rock specimen shows certain freeze-thaw cycle effect as the tensile strain at the center shows N=40>20>0>10 under 4 kinds of freeze-thaw cycles.