Better Cover-Ups

by Robert M. Koerner, (M.ASCE), Prof. and Dir.; Geosynthetic Research Inst. at Drexel University, Philadelphia, PA,
David E. Daniel, (M.ASCE), Civ. Engrg. Prof.; University of Texas at Austin, Austin, TX,

Serial Information: Civil Engineering—ASCE, 1992, Vol. 62, Issue 5, Pg. 55-57

Document Type: Feature article

Abstract: Designing the final cover for a solid waste landfill or remediation site is often trickier than designing its lining because a cover will undergo more unpredictable stress and distress during its life span. Engineers must pay special attention to the barrier component, as compacted clay does not necessarily make the best or cost effective barrier. Covers must perform one or several functions in addition to keeping water out of the contaminated material. Most covers are composed of five layers: the surface layer (soil, cobbles or paving), the protective layer (generally local soil), a drainage layer that reduces water pressure on the barrier layer, and a gas collection layer which must have a high in-plane gas flow rate. Of these, the barrier layer is the most critical and even though compacted clay is most often used, it is subject to freeze/thaw damage, penetration by roots and burrowing animals, and cracks due to desiccation and differential settlement. Combining compacted clay with a geomembrane, however, provides a barrier layer that will outperform other types, especially compacted clay used alone.

Subject Headings: Landfills | Coverings | Clays | Compacted soils | Membranes |

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