The deformation behaviors of soft clay under cyclic loading were investigated with constant loading frequency; however, the response frequency of the subgrade soil varied when the train passed by. Moreover, both deviator stress and confining pressure varied cyclically. Hence, two types of cyclic triaxial tests were conducted on saturated soft clay, in which the differences in deformation behaviors between constant and composite loading frequencies were analyzed, and the impacts of cyclic confining pressure and drained conditions were considered. The strain increment continuously decreased with the progress of the test under cyclic loading with constant loading frequency, while that first decreased, achieving the minimum value at the third loading stage, and then increased under cyclic loading with composite loading frequencies. Nevertheless, compared with the test results of cyclic triaxial tests with composite loading frequencies, the strain with constant loading frequency increased by 65.4% and 117.9% under undrained and partially drained conditions, respectively. The cyclic triaxial tests with constant loading frequency overestimated the strains under cyclic loading. The strain increments were greater in the first loading stage under undrained and partially drained conditions; however, the differences in strain increments between undrained and partially drained conditions in other loading stages can be ignored. Moreover, the effect of cyclic confining pressures was clarified under cyclic loading with composite loading frequencies: the strain ratio of cyclic confining pressures to constant confining pressures decreased from 0.870 to 0.723 as eta increased from 1.00 to 2.00 under undrained conditions, while it increased from 1.227 to 1.837 under partially drained conditions. Nevertheless, the ratios increased linearly with increasing eta under partially drained conditions, and decreased linearly under undrained conditions.

Frost damage is one of the main factors affecting the stability of canal slopes in cold regions. To alleviate the damage, laying protective layers during the construction process has become an indispensable measure. In this study, two slope models were constructed using polyester geotextiles (slope I) and composite geomembranes (slope II) as the protective layer. Additionally, the insulation board in the control group were laid on specific to examine their anti-frost effect. The temperature, frozen depth, and frost deformations of slope models during the freeze-thaw process were recorded and analyzed. Results suggest that the temperature of slope II is relatively lower than that of slope I in the freezing process. The temperature reduction at all monitoring sections of slope II are larger than that of slope I. The slope I exhibits a significant decrease in maximum frozen depth and maximum frost deformation. In particular, the with the maximum frost deformation is independent of the type of protective layer, which all occurs in the middle of the slopes. The maximum frost deformations of slope models are 33.60 mm and 37.69 mm, respectively after laying the polyester geotextiles and composite geomembranes. Therefore, the polyester geotextiles have more advantages in reducing frost deformation than composite geomembranes. Additionally, if the insulation board and polyester geotextiles are laid together inside the slope, the maximum frost deformation can be further reduced to 9.72 mm. This study will help in the design and construction of canal slopes in cold regions.