Differential Settlement Assessment of Landfill Liners in Karst Terrain—Voids in Soil beneath a Liner System

Modern US landfill regulations include provisions for the design of liner systems, including the liner itself, the overlying leachate collection system, and other features. An effective design includes the characterization of the subsurface soil and rock conditions and an understanding of the settlement response of the liner system during all phases of landfill development. Subsurface conditions that include karst geology and topography pose a significant challenge from the perspective of characterizing the subsurface and understanding the settlement response of the liner system to landfill loadings. This paper presents the results of a study performed by the authors to assess the differential settlements of landfill liner systems constructed over karst terrain due to post-construction collapse of a subsurface void at depth beneath a liner system. The differential settlement is caused by the raveling of soil overlying the void into the void. With regard to this symposium, this paper was prepared to specifically acknowledge the following contributions by Dr. Bonaparte: (1) Dr. Bonaparte has devoted significant efforts to study and report on the performance of landfill liner systems; and (2) Dr. Bonaparte has encouraged his colleagues to “think outside the box” and not to shy away from innovative solutions to problems.