Laboratory and In Situ Tests for Long-Term Hydraulic Conductivity of a Cement-Bentonite Cutoff Wall |
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Authors: | Kaushal Joshi Cedric Kechavarzi Kenneth Sutherland Man Yin Albert Ng Kenichi Soga Paul Tedd |
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Affiliation: | 1Ph.D. Student, Dept. of Engineering, Univ. of Cambridge, Cambridge CB2 1PZ, U.K. (corresponding author). E-mail: kdj22@cam.ac.uk 2Lecturer in Environmental Soil Physics, Cranfield Univ., Cranfield MK43 0AL, U.K. E-mail: c.kechavarzi@cranfield.ac.uk 3Deceased, formerly, Ph.D. Student, Dept. of Engineering, Univ. of Cambridge, Cambridge CB2 1PZ, U.K. 4Ph.D. Student, Dept. of Engineering, Univ. of Cambridge, Cambridge CB2 1PZ, U.K. E-mail: myan2@cam.ac.uk 5Professor, Dept. of Engineering, Univ. of Cambridge, Cambridge CB2 1PZ, U.K. E-mail: ks207@cam.ac.uk 6Formerly, Building Research Establishment, #1 Watford WD25 9XX, U.K. E-mail: tedd@ukf.net
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Abstract: | Slurry trench cutoff walls, constructed using self-hardening slag-cement-bentonite (Slag-CB), are the most common form of in-ground vertical contaminant barrier in the U.K., Europe, and Japan, and are increasingly being used in the United States. This paper presents a case study of the hydraulic conductivity evaluation of an 11-year-old Slag-CB wall material at a sulfate-contaminated site, using different in situ techniques and laboratory tests. The laboratory results suggest that the hydraulic conductivity of the samples, which vary in age from 4 weeks to 11 years, decreases with time for the first 3 years but then remains constant. The results indicate that the long-term performance of these containment walls is influenced by various parameters such as aging, the type/duration of contaminant exposure, mixing of surrounding soil during construction, and wall depth. Piezocone tests, packer tests, and self-boring permeameter tests were carried out in the field to determine the suitability of different in situ techniques and compare with the laboratory results. The hydraulic conductivity is affected by the type of in situ technique used and the geometric scale of the test section. |
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Keywords: | Bentonite Cement Containment Groundwater pollution Heterogeneity Hydraulic conductivity In situ tests Slurry walls |
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