液氮循环冷却对花岗岩物理力学特性的影响OA

[Purposes]Current researches on the impact of liquid nitrogen(LN2)cyclic cooling technology on the tensile properties and pore structures of high-temperature granite are still limited.There is a lack of detailed analysis of the variation patterns in physical and mechanical properties of granite under different temperatures and cyclic conditions.Therefore,further exploration is needed to investigate the effects of LN2 cooling cycles on the microstructure of granite.[Methods]In this study,the effects of high temperature(25-600℃)and LN2 cycling treatment on the physico-mechanical properties of granite were investigated through experiments.The evolutions of longitudinal wave velocity,tensile strength,porosity,and pore size distribution of granite under high temperature and LN2 cycling cooling were explored.[Results]The results indicate that with an increase in the num-ber of LN2 cooling cycles,the tensile strength and wave velocity of granite decrease significantly,while porosity and pore size increase significantly.Especially,after high-temperature treatment above 400℃,changes in the physico-mechanical properties are more pronounced.Additionally,by analyzing the differences in thermal expansion coefficients of mineral grains and the damage mechanism caused by internal temperature gradients within the rock,the reasons behind the significant damage to granite structure caused by LN2 cooling are revealed.[Conclusions]The findings provide experimental evi-dence for the application of cryogenic fracturing technology in geothermal energy development.