The cyclic fluctuation of reservoir water level makes soft rock in bank slope under cyclic seepage pressure and will bring certain effects on permeability characteristics of the soft rock. In order to obtain the relationship between the seepage pressure and seepage time, permeability tests were conducted on red sandstone specimens (from Three Gorges Reservoir Area, China) under cyclic seepage pressures by the self-developed equipment with the function to simulate cyclic fluctuation of reservoir water level. Experimental results show that the water infiltration of the sample was not stable in first three cycles, and it changed from 0.444 mL to 0.086mL. After three cycles, the water infiltration fluctuated between 0.060mL and 0.069mL. It can be drawn that the seepage velocity increase with the raise of pressure and it fit a four times polynomial in each cycle. The study indicates that increasing the seepage pressure appropriately can improve the seepage velocity, and greatly shorten the seepage time.

The problem of “difficult” freezing of the calcareous clay layer fractures in freezing pipes has been investigated. Based on the engineering background of the deep calcareous clay in the Yangcun Mine, model tests were carried out in order to conduct in-depth research on the development law of the freezing temperature field of this clay layer. The test results have shown that the calcareous clay has a freezing point of −1.3°C under the action of both the water and the soil’s chemistry and the supercooling temperature can be as low as −3.8°C because of its complex mineral composition causing poor thermal conductivity. This means that the calcareous clay will freeze slowly than the other layers of the soil. The time taking for the temperature fields to intersect is 2.5 h, which is equivalent to 127.6 days in the actual engineering. In the three sections, each temperature measurement point in the temperature field had an irregular saddle shape in the temperature space at the same time, and the ratio of the time between the formation and total melting of the frozen wall was 1 : 1.91. The development speed of the thickness of the frozen wall from 5 h to 16 h was 17.9 mm/h, and the development speed from 16 h to 70 h was 1.96 mm/h; corresponding to the actual development speed of the thickness of the frozen wall which were 0.0123 m/d and 0.0014 m/d, respectively. These speeds were significantly slower than the development speed of the thickness of the freezing wall of the general sandy clay layer, which were 0.0515 m/d in the early stage and 0.02 m/d in the later stage. The thin thickness and low strength of the frozen wall of the calcareous clay layer cause the fracture of the frozen pipes, which should be paid attention to in actual engineering construction.