Hydraulic Conductivity Prediction of Saturated Sand-Bentonite Mixtures
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ORIGINAL PAPER
Hydraulic Conductivity Prediction of Saturated Sand-Bentonite Mixtures K. K. Tripathi
Received: 16 June 2012 / Accepted: 17 December 2012 / Published online: 19 February 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract In this paper, models have been developed to predict the hydraulic conductivity of the saturated bentonite and saturated sand-bentonite mixtures. For these models, free swell void ratio of the bentonite is required which can be obtained using a simple test. It was observed that hydraulic conductivity of the saturated bentonite and saturated sand-bentonite mixtures could be predicted within 5 or 1/5 times of the measured values for most of the cases. Keywords Hydraulic conductivity Bentonite Sand-bentonite mixture Prediction
Gs k kb
kbe km LL M, p Vb Vf Vw
List of Symbols C, C1, C2 Numerical constants e Void ratio of the soil eb Bentonite void ratio of the sand-bentonite mixture ebc Condensed void ratio of the bentonite ebe Void ratio of the bentonite ef Free swell void ratio of the bentonite Gb Specific gravity of the bentonite
Wb Wd x xl xu cd cd(mod) cw cdl
K. K. Tripathi (&) Department of Civil Engineering, College of Engineering Pune, Shivajinagar, Pune 411005, India e-mail: [email protected]
cdu ev
Specific gravity of the sand Hydraulic conductivity of the soil Hydraulic conductivity of the bentonite at a void ratio equal to the eb of the sandbentonite mixture Hydraulic conductivity of the bentonite Hydraulic conductivity of the ideal sand bentonite mixture Liquid Limit of the bentonite Numerical constants Volume of the bentonite solid Volume of the saturated bentonite after full swelling Volume of the water in a unit volume of sand-bentonite mixture Weight of the dry bentonite Dry weight of the sand-bentonite mixture Bentonite content Lower limit of the bentonite content Upper limit of the bentonite content Dry unit weight of the sand-bentonite mixture Modified dry unit weight of the sandbentonite mixture Unit weight of the water Lower limit of the dry unit weight of the sand-bentonite mixture Upper limit of the dry unit weight of the sand-bentonite mixture Swelling strain (%) of the sand-bentonite mixture sample
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1 Introduction In the recent past, when suitable fine grained soils are not available for containing the waste, sand-bentonite liners are being used to construct landfill liners. In order to arrive at a suitable sand-bentonite mixture for the sand-bentonite liner, it is necessary to perform several permeability tests on the sand-bentonite mixtures with different bentonite contents. Each permeability test lasts from several days to several weeks and whole process may take several months (Chapuis 1990). Hence, in order to minimize the time and effort required in conducting permeability tests, several researchers have attempted to predict the hydraulic conductivity of sand-bentonite mixtures. Each prediction model has some advantages and some limitations. The model suggested by Chapuis (1990), is applicable when hydrated bentonite p
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