关键词: 膨胀性黏土, 热力耦合, 温度场, 冻胀力

Abstract:

To prevent the fracture of freezing pipe is an urgent problem in the formation of frozen wall in deep expansive clay layer. According to the soil properties of the deep thick expansive clay layer of a mine auxiliary shaft in Huainan mining area， distribution of the freezing temperature field and formation law of the frost heaving force are studied through the thermo-mechanical coupling calculation. When frozen for 152 days and 236 days， the average temperature of clay layer is -14.42 ℃， -16.58 ℃ and fine sand layer is -15.86 ℃， -17.32 ℃ respectively. The average temperature of clay layer is 1.44 ℃ and 0.74 ℃ higher than that of fine sand layer in the same period. The average thickness of the frozen wall in clay layer is 8.92 m and 10.25 m respectively， and that in fine sand layer is 9.54 m and 10.77 m respectively. The average thickness of the frozen wall in clay layer is 0.62 m and 0.56 m smaller than that in fine sand layer in the same period. Sand is easier to freeze and faster than clay. When frozen for 90 days， the average frost heaving force of the outer， middle and inner circles of the deep clay layer is about 1.1 times of that of fine sand layer in the same period. When the clay layer was frozen for 151 days， the average frost heaving force in the frozen wall surrounded by three circles of freezing pipes reached 81.1% of the initial ground stress， which was 1.16 times of the fine sand layer in the same period. When frozen for 236 days， the frost heaving force of inner circle of fine sand layer is 3.91 MPa， which is about 5.11% bigger compared with that of middle circle of 3.72 MPa， while that of inner circle of clay layer is 4.81 MPa， which is about 1.48% bigger compared with that of middle circle of 4.74 MPa. The average frost heaving force in the frozen wall surrounded by three circles of freezing pipes in clay layer is 88.6% of the initial ground stress， which is 1.28 times of that of fine sand layer in the same period. There is a significant non-uniformity in the frost heaving force at the deep expansive clay layer and the interface with the fine sand layer. The main position of the maximum frost heaving force is basically corresponding to the pipe break in the actual project excavation. It highlights that the non-uniform frost heaving force is the important reason for fracture of freezing pipes， which provides a reference for the design of similar frozen projects in the future.

Key words: expansive clay, thermo-mechanical coupling, temperature field, frost heaving force