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, of 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 separate 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, C-c, for the unamended backfill specimen was 0.24, whereas values of C-c for the zeolite-amended specimens were in the range 0.19 <= C-c <= 0.23. Similarly, the k for the unamended specimen based on flexible-wall tests was 2.4x10(-10) m/s, whereas values of k for zeolite-amended specimens were in the range 1.2x10(-10)<= k <= 3.9x10(-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. (C) 2012 American Society of Civil Engineers.