Abstract
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.
Highlights
Academic Editor: Shaohui Wang e 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 indepth research on the development law of the freezing temperature field of this clay layer. e 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. is means that the calcareous clay will freeze slowly than the other layers of the soil. e time taking for the temperature fields to intersect is 2.5 h, which is equivalent to 127.6 days in the actual engineering
Mathematical Problems in Engineering studied clay using the double coiled tube model test and the frost heave force that was generated during the formation of the frozen wall. e results showed that the frost heave force was closely related to the temperature and that it manifested as spatiotemporal inhomogeneity
Summary
Combined with the thickening of the water film and the presence of salt ions, the thermal conductivity of calcareous clay is affected for the following reasons: its freezing temperature is low (Figure 2); the freezing point of calcareous clay is −1.3°C; and its supercooling temperature is as low as −3.8. E presence of salt ions turns the frozen water between the soil particles into a salt solution; this lowers the freezing point of the clay and increases the adsorption strength of the water Under the same cooling conditions, a clay layer has poor thermal conductivity, the frozen soil develops slowly, its strength is low, the strength of the frozen wall is uneven in the vertical direction, and shear failure is prone to occur at the interface of adjacent soil layers
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