Study On The Triaxial Compression Failure Performance Of RCC Damaged By Freeze-thaw

With the rapid development of water conservancy,More and more countries and regions are building high concrete dams,and the RCC structure itself has many advantages,so the RCC dam will be the main type of high dams in the future.Because RCC dams are in a complex external environment,especially in high and cold regions,the RCC dams are subject to freeze-thaw damage throughout the year.Therefore,in this paper,the triaxial compression properties of RCC freeze-thaw damage is taken as the research object.By studying the macro,meso,and micro failure modes of triaxial compression of RCC under different freeze-thaw cycles,it provides theoretical support for RCC dams in cold regions.This paper mainly studies the following aspects:(1)Through the triaxial compression test after the freeze-thaw cycle of RCC,it is found that the freeze-thaw erosion of RCC is a progressive process from the surface to the interior.With the increase of the number of freeze-thaw cycles,the freeze-thaw damage of RCC becomes more and more serious,the mass loss rate showed a trend of decreasing first and then increasing,the thickness of the damaged layer gradually increased,and the triaxial compression damage of freeze-thaw damage RCC was also more and more serious.(2)The discrete-element software PFC3D was used to calibrate the me so-parameters of the RCC numerical model.It is found that eight different micro-parameters have different effects on the mechanical properties of RCC under the same confining pressure and loading speed,which provides reference for the calibration of the micro-parameters of the numerical model of RCC under the later freeze-thaw cycle.(3)Based on PFC3D software,a correct numerical model of freeze-thaw damage rolling is established.On this basis,the contact force,crack development and the final crack state between theparticles at two different stage points on the axial stress-strain curve of RCC are studied to analyze the meso-failure process of freeze-thaw damaged RCC under triaxial compression.It is found that at the first stage point,the maximum contact force between particles is related to the number offreeze-thaw of RCC,while at the second stage point,the maximum contact force between particles is related to the residual stress of RCC model,and the maximum contact force between mortar and mortar at different stage points is greater than the maximum contact force between coarse aggregate and mortar.The number of micro-cracks in RCC model is related to the freeze-thaw times of RCC,and the number of shear cracks at different stage points is significantly higher than that of tension cracks.In the second stage point,the number of fragments is related to the number of freeze-thaw(4)The microstructure of the interface transition zone of RCC under different freeze-thaw cycles is observed by SEM.It can be seen that the freeze-thaw effect has no obvious change on the micro structure of coarse aggregate.However,with the increase of freeze-thaw cycles,there are many cracks in the interface transition zone,resulting in the decrease of compactness and Mechanical properties of RCC.Therefore,in order to improve the frost resistance of RCC,the strength of transition zone of RCC interface can be considered...