Consolidation and Hydraulic Conductivity of Zeolite-Amended Soil-Bentonite Backfills

The effect of zeolite amendment for enhanced sorption capacity on the consolidation behavior and hydraulic conductivity, k ,o f a representative soil-bentonite (SB) backfill for vertical cutoff walls was evaluated via laboratory testing. The consolidation behavior and k of test specimens containing fine sand, 5.8% (dry weight) sodium bentonite, and 0, 2, 5, or 10% (dry weight) of one of three types of zeolite (clinoptilolite, chabazite-lower bed, or chabazite-upper bed) were measured using fixed-ring oedometers, and k also was measured on sep- arate specimens using a flexible-wall permeameter. The results indicated that addition of a zeolite had little impact on either the consolidation behavior or the k of the backfill, regardless of the amount or type of zeolite. For example, the compression index, Cc, for the unamended backfill specimen was 0.24, whereas values of Cc for the zeolite-amended specimens were in the range 0:19 ≤ Cc ≤ 0:23. Similarly, the k for the unamended specimen based on flexible-wall tests was 2: 4×1 0 � 10 m=s, whereas values of k for zeolite-amended specimens were in the range 1: 2×1 0 � 10 ≤ k ≤ 3: 9×1 0 � 10 m=s. The results of the study suggest that enhancing the sorption capacity of typical SB backfills via zeolite amendment is not likely to have a significant effect on the consolidation behavior or k of the backfill, provided that the amount of zeolite added is small (≤ 10%). DOI: 10.1061/(ASCE)GT.1943-5606.0000566. © 2012 American Society of Civil Engineers.