Centrifuge and Numerical Study on the Behavior of Clay-Based Landfill Covers Subjected to Differential Settlements

Abstract

The objective of this paper is to evaluate the deformation behavior of clay-based landfill covers subjected to differential settlements through centrifuge model studies and finite-element analyses (FEA). A series of centrifuge tests were performed on model soil barriers subjected to continuous differential settlements through a motor-based differential settlement simulator by varying the thickness of the soil barrier with and without overburden equivalent to that of landfill coves at 40 gravities. In addition, a parametric study was carried out numerically by varying the thickness of the soil barrier and overburden pressure by using PLAXIS, a geotechnical finite-element code. The modeling considerations adopted in FEA were developed such that they are close to the centrifuge model tests in prototype dimensions. Differential settlements in FEA were assigned by using predefined displacement profiles. Results from centrifuge model tests deduce that both 0.6 and 1.2 m thick soil barriers were observed to experience full-depth cracks at the zone of maximum curvature and fail to serve the basic purpose of an effective hydraulic barrier. The results from FEA indicate the development of higher values of tensile stresses and strain extending throughout the thickness of the soil barrier at the zone of maximum curvature, which indirectly advocate the possibility of formation of tension cracking when the generated tensile stresses caused by deformation exceed the permissible tensile strength of the soil barrier material. The magnitude of the horizontal tensile stress along the top surface of the soil barrier at the zone of maximum curvature was found to be suppressed with an increase in the value of overburden pressure. When the soil barrier was subjected to an overburden pressure in the range of 50–75 kPa, there exists a complete transformation of tensile stresses to compressive stresses, which indirectly suggests that there can be no prospects of development of tension cracks even at a distortion level of 0.125.