The Influence of Hydraulic Gradient and Rate of Erosion on Hydraulic Conductivity of Sand-Bentonite Mixtures
- 22 September 2006
- journal article
- research article
- Published by Taylor & Francis Ltd in Soil and Sediment Contamination: An International Journal
- Vol. 15 (5), 481-496
- https://doi.org/10.1080/15320380600847815
Abstract
The use of sand-bentonite mixtures as liner materials for waste disposal is very common. In the laboratory, this study investigated hydraulic conductivities of such mixtures at different hydraulic pressure (hydraulic gradient), dry unit weights, and bentonite contents. The bentonite content and the dry unit weight of the samples were both important factors, significantly affecting the hydraulic conductivity of the liner material. A bentonite content of 5% was found to be sufficient in reaching a hydraulic conductivity under 10−9 m/s, when the liner material was compacted under near optimum moisture content. Nevertheless, hydraulic conductivity was found to increase with hydraulic pressures, especially for the 5% bentonite mixtures subjected to pressure above 40 kPa, suggesting some degree of internal erosion (washing out of particles). Therefore, this paper discuses the influence of internal erosion of the mixtures under a given hydraulic gradient, on the final value of k. The internal erosion of the tested mixtures was found to be influenced mainly by porosity, which can be reduced by properly selecting the sand particle size distribution and the bentonite percentage. Furthermore, this study proposed an empirical expression to predict the risk of internal erosion in the sand-bentonite mixtures, and therefore of k being higher than planned. This expression can be used for designing bentonite content and compaction to achieve very low permeability.Keywords
This publication has 16 references indexed in Scilit:
- SRICOS: Prediction of Scour Rate in Cohesive Soils at Bridge PiersJournal of Geotechnical and Geoenvironmental Engineering, 1999
- La migration des particules fines comme approche d’explication du mécanisme de l’effondrement des solsRevue Française de Géotechnique, 1998
- The Clogging of Nonwoven Geotextiles With Cattle Manure SlurriesGeosynthetics International, 1998
- Design and construction of sand-bentonite liner for effluent treatment lagoon, Marathon, OntarioCanadian Geotechnical Journal, 1997
- Microstructural Changes in Sand-Bentonite Soils when Exposed to AnilineJournal of Geotechnical Engineering, 1995
- Washing of Bentonite in Laboratory Hydraulic‐Conductivity TestsJournal of Environmental Engineering, 1994
- Hydraulic conductivity of compacted bentonite–sand mixturesCanadian Geotechnical Journal, 1992
- Impact of molding water content on hydraulic conductivity of compacted sand-bentoniteCanadian Geotechnical Journal, 1992
- Sand–bentonite liners: predicting permeability from laboratory testsCanadian Geotechnical Journal, 1990
- Internal stability of granular filtersCanadian Geotechnical Journal, 1985