| Roller compacted concrete(RCC)DAMS have been widely used in many countries due to their advantages of low construction cost,low cement consumption and fast construction speed.In recent years,RCC DAMs have also been used in the cold regions such as northeast and Northwest China,and its long-term service performances.Given the importance of the mechanical properties of cold regions RCC under dynamic load,combined with the means in the macro and meso levels,the paper conducts the rapid freezing-thawing test and the dynamic mechanical loading experiment respectively to study the effect of freezing-thawing,strain rate and confined pressure on the mechanical properties of RCC.With the help of CT,the meso mechanism for the RCC damage is deeply studied.This study can provide a reference for improving the long-term service performance of RCC under complex coupled freezing-thawing and dynamic loading condition in cold regions,and also for the application of RCC construction technology in cold regions.The mainly research contents are as follows:(1)RCC mass loss increases with the increase of freezing-thawing cycles.After 25freezing-thawing cycles,the mass loss rate is 0.26%.When freezing-thawing cycles increases to 75,the accumulated mass loss reaches to 2.57%,which is far less than the national standard value of 5%.(2)The slopes of RCC stress-strain curve in elastic stage and local deformation stage show the similar increasing trend with an obvious peak point.(3)Under the same confining pressure,the peak strain is positively correlated with the number of freezing-thawing cycles and the acceleration of strain rate;with the same freezing-thawing cycle,the confining pressure effect of high strain rate increases the peak strain more significantly.(4)For the compressive strength of RCC,strain rate shows the maximum influence,followed by confining pressure,and freezing-thawing shows the minimum influence.(5)After freezing-thawing cycle test,the porosity of RCC increases linearly,and the porosity growth rate of 25 and 50 freezing-thawing times is 27%and 63.3%,respectively.After freezing and thawing,the proportion of pores with different pore sizes increases.The number of pores with pore volume less than 0.01mm~3 accounts for the largest proportion of the total number of pores,and the number of pores with pore volume greater than 10mm~3accounts for the smallest proportion.Most of the pores are in the range of less than 1mm~3. |
