In order to investigate the influence of different temperature difference freeze-thaw cycle on the microstructure of rock body of open-pit coal mine slope under the action of constant load,the self-developed TCDR-Ⅰtemperature-stress cou-pling test system was used to obtain the change law of internal pore and pore throat distribution of water-saturated sandstone before and after freeze-thaw cycle through the nuclear magnetic resonance test and acoustic wave detection and analysis tech-nology after the action of constant load and freeze-thaw cycle with different temperature difference.The results show that as the lower limit temperature of freeze-thaw cycle decreases,the internal damage factor of water-saturated sandstone increases gradually.The porosity increase ratio of freeze-thaw sandstone increases exponentially as the lower limit temperature decrea-ses,and the larger the temperature difference is,the influence on the pore structure is more significant.The increase of small pore throats and the decrease of medium and large pore throats of the loaded sandstone during the freeze-thaw cycle increase linearly with the decrease of the lower limit temperature.The fractal dimensions of the pore structure in the sandstone are neg-atively correlated with the lower limit temperature,and the pore structure of loaded sandstone during freeze-thaw cycle pres-ents multiple fractal characteristics,with the fractal dimension of small pores increasing from 2.308 at-10 ℃～20 ℃ to 2.558 at-40 ℃～20 ℃,and the fractal dimension of pore throats ranges from 2.967 to 2.983.The research results can provide a reference for the study of seasonal damage mechanism and fracture evolution of rocky slopes in open-pit mines in cold regions.
freeze-thaw temperature differencenuclear magnetic resonanceporositypore throatfractal dimension
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