Physical modeling of mechanical responses of HDPE pipes and subsurface settlement caused by land subsidence

Failure of buried high-density polyethylene (HDPE) pipes caused by land subsidence is often encountered in the engineering practice. The main reason is the additional stress and strain on the buried HDPE pipes induced by the land subsidence. Most of the previous studies focus on the mechanical responses of HDPE pipes to a mobilized zone in the ground with a specific size. However, no analytical methods are available to evaluate the pipe responses during the process of ground movement. In this study, coarse sand is filled in a custom-made pipe-soil interaction testing system, and the lowering of the adjustable bottom of the test box is used to simulate the effect of land subsidence. During the test process, the earth pressure, deformation of HDPE pipes and subsurface settlement above the pipe are measured. The test results demonstrate that (1) The vertical deflection distribution of HDPE pipes in the longitudinal direction agrees well with the modified Gaussian curve; (2) The vertical earth pressure on the pipe crown increases with the lowering of the bottom plates, and the soil arching ratio at the pipe crown increases from 0.7 to 2.05, which indicates that negative soil arching occurs above the pipe during the ground movement; (3) The effect of the ground movement on the deformation of HDPE pipes gradually decreases with the decrease of the thickness of soil cover; (4) The magnitude of the subsurface settlement above the pipe is limited more significantly when the bending stiffness of the pipe increases.