Document Type

Conference Paper

Publication Date

2018

Conference/Sponsorship/Institution

8th International Congress on Environmental Geotechnics

Location

Hangzhou, China

Department

Civil and Environmental Engineering

Abstract

The objective of this paper is to present a comparison of measured hydraulic conductivities (k) for soil-bentonite (SB) backfill within a 60-m-long section of a 200-m-long, 7-m-deep cutoff wall constructed and instrumented for studying SB backfill properties and variability at the field scale. Backfill k was measured using flexible-wall tests (70-mm diameter) on remolded specimens prepared from surface grab samples collected during construction; flexible-wall tests on undisturbed specimens collected from the wall; larger-scale rigid-wall tests (150-mm diameter) on remolded specimens prepared from grab samples; and slug tests conducted within the wall. Applied effective stresses in the laboratory tests ranged from 4–35 kPa, encompassing the range of in-situ stresses measured in the backfill after load transfer and consolidation (8–13 kPa). The results indicate low spatial variability in k for a given test type, consistent with the observed homogeneity of the backfill. Modest variability in k was observed among the different test types, with the slug tests and rigid-wall tests generally yielding slightly higher k relative to the flexible-wall tests at field-representative stresses.

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