Abstract: In order to study the mechanical properties and damage mechanism of rock under high temperature,the uniaxi al compression simulation of sandstone under real-time high temperature was carried out by particle flow software PFC3D.The stress-strain characteristics and crack development process of sandstone at different temperatures are clarified,and the variation law of peak stress,peak strain and crack development of sandstone with temperature is clarified.Based on the mechanical prop erties,the thermal damage mechanism of sandstone is clarified,and the damage statistical constitutive model of sandstone under high temperature is established.The results show that the peak stress and peak strain of sandstone decrease with the increase of temperature in the temperature range of 0~25 ℃.In the temperature range of 25~150 ℃,the peak stress and peak strain have the same change trend,which increases first and then decreases.In addition,the toughness index is introduced to reflect the an ti-failure ability of sandstone,and its change rule is the same as the evolution trend of peak stress.As the temperature increa ses,the thermal stress will promote the propagation of the original crack and generate new cracks,and the expansion of the in ternal particles will further accelerate the crack development and eventually form the overall damage.Finally,the damage statis tical constitutive model of sandstone under high temperature is constructed,and the rationality of the model is verified by the simulation results.This study can provide theoretical support for the analysis of mechanical properties of sandstone under high temperature environment.

Key words: hightemperature,mechanicalproperties,toughnesscoefficient,constitutivemodel,Weibulldistribution