Model test study on mechanical properties of pipe under the soil freeze-thaw condition

Buried pipe is an important structure underneath embankment. In the frozen soil region, the destruction of pipe will directly affect the service life and benefit of road. Based on the effect of freeze-thaw action of embankment filling on pipes in the field, model tests on shallow buried PVC (Polyvinyl chloride) pipe were carried out in the temperature control laboratory. Variation of stress and strain of pipe, earth pressures around pipe and deformations of pipe were investigated under different filling loads, different layers of geogrid, symmetrical and asymmetrical freeze-thaw of soil around the pipes. The test results show that most of the upper half of the pipe is in compressive strain state, except for the 0° measuring point on the crown vertex of the pipe. And most of the lower half of the pipe is in tensile strain state. The maximum compressive stress and the maximum tensile stress are at points with an angle of 45° and 135° from the vertices of pipe, respectively. When symmetrical frost-heave of the soil occurs in the surrounding pipe, load reduction measures should be taken at the crown of the pipe. When asymmetrical frost-heave of the soil occurs in the surrounding pipe, the differential horizontal deformation of the pipe between its left and right halves is obvious, therefore the earth pressures on the lateral of the pipe should be monitored emphatically. The geogrid installed above the pipe effectively reduces the eccentric load on the pipe. The thaw-settlement of frozen soil has the greatest impact on the deformation of shallow buried pipes, which is more threatening to cause pipe damage. The test results can provide a reference for engineering design, construction and maintenance of shallow buried pipe under the soil freeze-thaw condition.