Experimental Study On The Damage Characteristics Of Granite Under The Effect Of Freezing And Thawing Cycles

China's cold regions are widely distributed and rich in resources.In the rapid development of China today,the development and utilization of its cold regions resources become extremely important.The stability and safety of rock are very important and necessary to study the mechanical properties of rocks under freeze-thaw.In this paper,the granite is taken as the research object,and the number of freeze-thaw cycles is used as a variable factor.The freeze-thaw cycle test is carried out on the granite to determine the longitudinal wave velocity and quality of the rock after each group of freeze-thaw cycles.The axial compression test analyzes the changes of rock quality,longitudinal wave velocity and mechanical parameters before and after freezing and thawing,and studies the damage evolution and constitutive relationship of frozen rock based on the analysis of frozen rock data and damage mechanics.The following conclusions are obtained:(1)The characteristics of the frozen rock in the cold region,the damage mechanism,and the influencing factors of freezing and thawing are analyzed.The types of disasters caused by freezing and thawing are classified,and the intensity of the freezing and thawing regions in China is classified according to the degree of erosion during freezing and thawing.(2)Through the freeze-thaw test,the mass and wave velocity of the rocks before and after each freeze-thaw treatment were measured,and their changes were analyzed.It was found that with the continuous increase of the number of freeze-thaw cycles,the quality of the granite gradually increased.The P-wave velocity has been decreasing.(3)In order to explore the changes in the mechanical properties of rocks after freeze-thaw,uniaxial longitudinal loading tests were performed on each group of freeze-thaw treated rock samples,and some mechanical parameters of each group were compared and analyzed.With the continuous increase of the number of time cycles,the mechanical parameters such as the peak strength and elastic modulus of the rock have been reduced.At the same time,in order to explore the freeze resistance of the rock,the freeze resistance of the granite during freezing and thawing is analyzed.The freezethaw resistance increased with the increase in the number of freeze-thaw cycles,but the freeze-thaw coefficients of all rock samples after this freeze-thaw were maintained above 80%,indicating that the rock has a strong freeze-thaw resistance.The damage to granite is minor.(4)To investigate the damage evolution law of granite after freeze-thaw,the damage factors of wave velocity,elastic modulus and peak stress of the rock after freezing and thawing are calculated and analyzed.Damage evolution equation of granite under cyclic loading.