Field Performance of Compacted Clay Liners

Abstract

A database consisting of 85 full-scale compacted clay liners was assembled to evaluate field hydraulic conductivity K_F. Large-scale field hydraulic conductivity tests were conducted on each liner. All of the clay liners were intended to achieve K_F ≤ 1 × 10⁻⁷ cm/s, but only 74% succeeded in meeting this objective. The important factors affecting K_F are the soil wetness relative to the line of optimums and the number of lifts or the thickness of the liner. Poor correlation exists between K_F and hydraulic conductivities measured in the laboratory (K_L) on field-compacted samples (especially for liners with K_F > 10⁻⁷ cm/s compacted at lower water contents relative to the line of optimums), percent compaction, and index properties representative of composition (e.g., Atterberg limits and particle size fractions). The findings indicate that (1) compacted clay liners having K_F ≤ 10⁻⁷ cm/s can be constructed with a broad variety of clayey soils; (2) the primary emphasis should be ensuring compaction is primarily wet of the line of optimums; (3) less emphasis should be placed on other traditional measures such as percent compaction, K_L, and index properties; and (4) liners that are thicker or have a greater number of lifts tend to have lower K_F.