Compressibility and Hydraulic Conductivity of Sand/Clay-Bentonite Backfills

Soil-bentonite (S-B) vertical cutoff walls are effective and economical as engineering barriers for contaminant containment. Water content higher than liquid limit (wL) is needed for S-B backfills to achieve a target slumps, ranging from 100 to 150 mm, for the purpose of improving constructability. A series of one-dimensional consolidation tests was performed to evaluate the compressibility and hydraulic conductivity of S-B backfills. Kaolin and sand were selected to simulate in-situ soils. The results indicate that BC critically controls the compressibility and hydraulic conductivity (k) of S-B backfills. The effect of grain size of sand on compression index (Cc) and k is insignificant. Cc increase with an increase in initial water content (w0). However, the effect of w0 on the compressibility can be eliminated by using compression ratio (CR). In addition, values of k are further discussed based on Nagaraj's generalized state parameters (e/eL) and an empirical method for predicting k using void ratio (e) and wL.