Study on Thermal Shrinkage Characteristics of Improved Coarse-Grained Soil Fillers for High-Speed Railway Embankments in Temperature Cycles

In view of the high requirement for smooth operation of high-speed railway in cold regions, two representative temperature difference environments in Hebei region were selected and the effects of filler types, temperature cycles and temperature difference intervals on thermal shrinkage strain characteristics of improved coarse-grained soil fillers were studied. The results indicated that the fillers improved with cement had larger thermal shrinkage strain and thermal shrinkage coefficients, and the mixing of fly ash reduced the maximum thermal shrinkage strain and average thermal shrinkage coefficients, but the mixing ratio of fly ash could not be too large, the maximum thermal shrinkage strain of the fillers increased first and leveled off after the third cycle. Comparisons of thermal shrinkage coefficients of improved fillers that had undergone temperature cycles in different temperature intervals, it was found that the sensitivity of improved fillers to temperature changes decreased after experiencing multiple temperature cycles. The ratios of strain loss and strain recovery were proposed. Furtherly, it was concluded that mixing a little amount of cement into the improved fillers could improve the strain recovery ratio, but the effect was not obvious in the environment of -20 ℃ to 30 ℃. It was suggested that in the construction of high-speed railway in Hebei province, the improved coarse-grained soil fillers with the cement mixing ratios of 3% to 5% and fly ash mixing ratios of 12% to 20% should be used.