Properties and Application of Cement Improved Loess under Low Temperature Environment in Cold Region
According to the cold climate and low annual average temperature in cold regions of China,the field curing conditions of cement improvement of collapsibility loess under low temperature,room temperature,and medium temperature were simulated at 5℃,10℃,20℃,and 30℃,respectively.Based on laboratory experiments,this study analyzed the effects of curing temperature,cement content,and curing age on RCBR,unconfined compressive strength,and dynamic resilience modulus of cement improved loess.The effects of cement content and curing temperature on freeze-thaw durability and erosion resistance of cement improved loess were studied by the freeze-thaw cycle test and dynamic water erosion test.Combined with the laboratory results,the 4% and 5% cement improved loess were applied to fill the upper and lower roadbed of the expressway,with a test of the elastic modulus of the top surface of the roadbed,the dynamic elastic deflection of FWD and the static elastic deflection of Beckman beam in the test section.Finally,the fitting relationships between the elastic modulus of the top surface of the roadbed and the measured bending as well as the dynamic and static bending were established.The results show that the mechanical indexes such as RCBR,unconfined compressive strength,and dynamic resilience modulus of cement improved loess increase continuously with the rise of curing temperature and cement content.After 9 freeze-thaw cycles,the dynamic resilience modulus of cement improved loess tends to be stable.Considering the freeze-resistance,freeze-thaw durability,and economy of cement improved loess,the appropriate cement content is recommended to be 4% ‒5%,and the reduction coefficient of dynamic resilience modulus of cement improved loess constructed at 5 and 10℃in cold regions can be 0.80‒0.85 and 0.90‒0.95.The fitting relationship between the measured deflection of BB(LBB)and the measured deflection of FWD(LFWD)is LBB=1.166×LFWD.
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