Role of overconsolidation on sand-geomembrane interface response and material damage evolution

The behavior of high-density polyethylene (HDPE) reinforcement elements is critical to the overall performance of many geotechnical structures including landfills, retaining walls, embankments, and shallow foundations. The reinforcement elements, which may consist of manufactured sheets or strips, must be properly installed in order to transfer stresses from areas of concentrated loading to reinforcing zones. While attention is given during construction to avoid contact damage of reinforcement elements, the construction process exerts stresses on the reinforcement element that may substantially exceed the stresses acting throughout the structure's service life. This paper examines the influence of overconsolidation of HDPE reinforcement elements on interface performance through examination of its effect on sand-smooth geomembrane interfaces. A range of overconsolidation and operational normal stress values are selected based on conditions typically present in practice. Results show the peak friction coefficient to increase substantially with overconsolidation magnitude while the effect on the residual friction coefficient is minimal. The magnitude of the increase in peak friction coefficient is shown to be dependent on both the damage induced by the smooth geomembrane and the degree to which sand particles adjacent to the interface undergo damage in the form of breakage during shear. The damage induced by the smooth geomembrane and the sand particles are presented in terms of the level of overconsonsolidation, confinement stress during shear, and particle characteristics such as angularity and hardness.