Interaction law and mechanical characteristics between pipe and soil during frost heaving

In order to study the mechanism characteristics and the interaction law between pipe and soil during frost heaving, the silty clay with high frost susceptibility and the stainless steel pipe were used as materials, and the test was carried out in a small environmental model testing machine without external water supply. Firstly, the resistance strain gauges were pasted to the surface of pipe, then the pipe and support were placed in the open heat preservation box. Secondly, the soil sample was filled into the open heat preservation box while the sensors including temperature, moisture and soil pressure sensors were arranged at each measuring point synchronously. Finally, the variables such as temperature, water content, pressure, frost heave, deformation and stress of pipe were monitored in real time during the testing. Then the testing data collected from the process of frost heaving which lasts for 70 h was analyzed and discussed. The results show that the essence of pipe restraining frost heave during frost heaving is to restrain the moisture migration in soil. The distribution law of unfrozen water content and the water content after frost heaving proves the occurrence of moisture migration in soil. The interaction between pipe and soil leads to coordinate changes and keeps a dynamic balance all the time. Frost heaving causes the pipe deformation while the pipe restrains the frost heave of soil. The deformation of pipe and the distance from pipe determine the constraint strength to frost heaving. The smaller the pipe deformation, the greater the constraining rate, the larger the soil pressure, the smaller the moisture migration and the smaller the frost heave. However, at the same time, the frost heave on both sides of pipe is obviously larger than that below the pipe. The farther away from the pipe, the smaller the constraining rate, the smaller the soil pressure, the greater the moisture migration, and the larger the frost heave. The soil pressure increases with time, and increases exponentially with constraining rate, but decreases exponentially with frost heave. Frost heaving causes pipe stress, and the most disadvantageous stress distribution position is in 4/8 section of the pipe. The existence of circumferential stress indicates the section of the pipe deformation, so the effect of circumferential stress cannot be ignored in the analysis when the pipe actes on a larger frost heaving force or external load. © 2020, Central South University Press. All right reserved.