Estimating Hydraulic Conductivity of Compacted Clay Liners

A database is described that contains laboratory measurements of hydraulic conductivity and associated soil properties that were extracted from construction reports for compacted soil liners. The database contains measurements conducted on a wide variety of soils from 67 landfills in North America. The database was used to evaluate relationships between hydraulic conductivity, compositional factors, and compaction variables and to identify minimum values for soil properties that are likely to yield a geometric mean hydraulic conductivity ≤1×10-7cm/s. A graphical analysis suggests that a geometric mean hydraulic conductivity≤1×10-7cm/s can be achieved if the liquid limit ≥20, the plasticity index ≥7, the percent fines (<No. 200 sieve) ≥30%, and the percent clay (<2 μm) ≥15%. A multivariate regression equation was also developed that can be used to estimate the geometric mean hydraulic conductivity as a function of soil composition and compaction conditions.