Hydraulic Conductivity of Vertical Cutoff Walls

Evans, JC

doi:10.1520/stp23885s

Cited by 48 publications

(14 citation statements)

References 5 publications

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“…Compressibility of the bentonite slurry is important in the design of a slurry wall, as it should provide a rigid skelton with minimum settlement (D'Appolonia, 1980;Ryan, 1987;Evans, 1993Evans, , 1994. The consolidation behaviours of conventional soil bentonite backfill and bentonite slurry have been studied extensively by many researchers (McCandless & Bodocsi, 1988;Evans, 1993;Filz, 1996;Yeo et al, 2005aYeo et al, , 2005b.…”

Section: Introductionmentioning

confidence: 99%

Compressibility behaviour of bentonite and organically modified bentonite slurry

Sreedharan¹,

Puvvadi²

2013

Géotechnique

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Bentonite in slurry walls needs to be amended with organo-clay to control the migration of organic contaminants. Consolidation behaviour of the slurry is important because it will reduce the total effective stress owing to mobilisation of frictional force between the side wall of the trench and the slurry. Compressibility of the slurry of bentonite is expected to undergo significant changes owing to amendment with organo-clay and according to the nature of the fluid. Standard one-dimensional consolidation tests were carried out on slurries of bentonite, organo-clay and their mixtures by remoulding them to their respective liquid limit consistency with water as well as fluids of low polarity, such as carbon tetrachloride, and inundating with different fluids. Organo-clay and its mixture with bentonite when moulded with water exhibit lower compressibility than bentonite in any pore fluid, but their compressibility increases when moulded with carbon tetrachloride and inundated with the same fluid. These changes in the compressibility of bentonite amended with organo-clay are explained by particle rearrangements, changes in the development of the diffuse double layer and contribution from the water adsorbed in the inter-lamellar space of the clay.

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Section: Introductionmentioning

confidence: 99%

Compressibility behaviour of bentonite and organically modified bentonite slurry

Sreedharan¹,

Puvvadi²

2013

Géotechnique

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“…e k c of back lls permeated with Pb(NO 3 ) 2 solutions is shown in Figure 5, for a certain Pb concentration; the k c of back lls decreases with the increasing PAC content of back lls; and for a given PAC content, the k c of back lls increases with Pb concentration. Under applied pressure 100 kPa, the k c of PSB-0.6 was maintained lower than 10 −9 m/s, regardless the Pb concentration variation, which is below the limit designed value of hydraulic conductivity for typical sand-bentonite back lls in vertical cuto walls [1,33]. e k c /k w of PSB-0.6 is lower than 10 permeated with concentrated Pb(NO 3 ) 2 solution (100-500 mM), indicating that the k c of PSB-0.6 has no obvious increase.…”

Section: E Optimum Polymer Dosagementioning

confidence: 83%

Hydraulic Conductivity of Polymer‐Amended Sand‐Bentonite Backfills Permeated with Lead Nitrate Solutions

Shen

Wei

2018

Advances in Civil Engineering

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Hydraulic conductivity of sand-bentonite (SB) backfills amended with polyanionic cellulose (PAC) to lead nitrate (Pb(NO3)2) solutions was evaluated experimentally in this study. PAC-amended sand-bentonite (PSB) backfills were synthesized by mixing sand-bentonite mixture with 0.3 to 1.2% dry PAC (by total dry mixture mass) and mixed with a certain weight of conventional bentonite (CB) slurry. The rheology properties including the filtrate loss, viscosity, density, and pH testes of slurry with various bentonite dosages were measured to determine the reasonable CB dosage of slurry. The slump tests on PSB backfills with various mass slurries were conducted to determine the corresponding water content of backfills with slump 125 ± 5 mm. Under the applied pressure 100 kPa, the hydraulic conductivity to Pb(NO3)2 solutions (kc) of PSB backfills with various PAC contents was evaluated based on the modified filter press (MFP) tests, to ascertain the optimum PAC content of PSB backfills when permeated with Pb(NO3)2 solutions. Index properties, including the specific gravity (Gs) and liquid limit (wL) of PSB backfills, were measured after MFP tests. The MFP tests for PSB backfills were then conducted under various applied pressures to obtain the relationship between void ratio (e) and hydraulic conductivity of backfills. Finally, the flexible-wall permeability test (FWP test) under osmotic pressure 100 kPa was conducted to verify the effectiveness of the MFP test. The results indicate that slurry with 8% bentonite dosage is the reasonable choice in slurry wall construction. PSB has lower GS and higher wL compared to SB; increasing Pb concentration leads to GS of PSB increased and wL of PSB decreased. PSB with 0.6% PAC content is supposed as the optimum proportion of backfills when permeated with concentrated Pb(NO3)2 solution. PAC adsorbs large amount of bound water, which leads to higher water content (w) and e of PSB backfills, while lead ions (Pb) cause the diffuse double layer (DDL) of bentonite compressed and e of PSB backfills reduced. The kc of PSB-0.6 remains lower than 10−9 m/s and increases less than 10 times though the Pb concentration was up to 500 mM, demonstrating that the hydraulic performance of backfills can be improved effectively in Pb(NO3)2 solution by the additive PAC. The comparison results between k from MFP tests and FWP tests show that the MFP test is an effective and easy evaluation of hydraulic conductivity of backfills.

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“…Fine materials are particles that passed through #200 sieve during the particles size analysis test (ASTM D422). Evans [17] agrees that the cut-off wall mix must contain at least 15% fines to garner a low coefficient of permeability (commonly less than 9.9x10-7 cm/s) because the percentage of fines present affects the hydraulic conductivity [18].…”

Section: Index Properties and Chemical Propertiesmentioning

confidence: 99%

Linear Optimization of Soil Mixes in the Design of Vertical Cut-Off Walls

Dungca¹,

Galupino²,

Sy³

et al. 2018

GEOMATE

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ABSTRACT:In order to prevent the contamination of surrounding groundwater in a landfill, cut-off walls were recommended. Cut-off walls are walls utilized when there is a need to restrict horizontal movement of liquids. Currently, the factors in designing cut-off walls are effective permeability, and relatively inexpensive materials in containing contaminants. It was suggested to provide a mix of 96% soil and 4% bentonite in the design of cut-off walls, but bentonite is relatively expensive, thus the viability of fly ash as a replacement for bentonite was considered. Soil mixtures were proposed and rigorous laboratory tests was performed to determine the individual properties. Tests such as specific gravity tests, Atterberg limit tests (liquid limit, plastic limit and plasticity index), emax and emin test/relative density tests, particle size analyses, microscopic characterizations, elemental composition tests and permeability tests were performed to garner data, and were utilized for the model. A linear optimization model was generated to achieve the least cost with the minimum required permeability. The minimum permeability requirement for the cut-off wall was achieved by providing various mixtures for soil-bentonite-fly ash.

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Hydraulic Conductivity of Vertical Cutoff Walls

Cited by 48 publications

References 5 publications

Compressibility behaviour of bentonite and organically modified bentonite slurry

Compressibility behaviour of bentonite and organically modified bentonite slurry

Hydraulic Conductivity of Polymer‐Amended Sand‐Bentonite Backfills Permeated with Lead Nitrate Solutions

Linear Optimization of Soil Mixes in the Design of Vertical Cut-Off Walls

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