Study on the Hydraulic Conductivity of Sand-Bentonite mixtures used as Liner System of Waste Landfill

A liner system such as liner sheet underlying impermeable soil layer having hydraulic conductivity less than 1*10-7 cm/s and a thickness larger than 100 cm is often used in china. As there is very little natural clay having such low permeability, bentonite is usually mixed into sand to decrease the permeability. In this paper, the compaction tests and permeability testing using flexible-wall permeameter are conducted. The test results show that the value of critical benonite ratio depends on bentonite ratio, and the hydraulic conductivity of the sand mixed with critical bentonite ratio for distilled water shows of the order of 1*10-8 cm/s that satisfies the china standard requested as compacted soil liner of waste landfill. Finally, the permeability testing used leachate including calcium component was conducted.

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A method to assess risk reduction when utilizing geosynthetic clay liners (GCLs) with compacted soil liners

Canadian Geotechnical Journal ◽

10.1139/t10-055 ◽

2011 ◽

Vol 48 (1) ◽

pp. 146-161 ◽

Cited By ~ 3

Author(s):

W. T. Menzies ◽

G. A. Fenton ◽

C. B. Lake ◽

D. V. Griffiths

Keyword(s):

Hydraulic Conductivity ◽

Analytical Solution ◽

Compacted Clay ◽

Geosynthetic Clay Liners ◽

Probability Of Exceedance ◽

Compacted Soil ◽

Liner System ◽

Soil Liners ◽

Soil Liner ◽

Random Field Simulation

This paper presents an analytical solution developed to estimate probabilities of “failure” or advective flux “exceedance” for the case of a spatially variable geosynthetic clay liner (GCL) situated over a spatially variable compacted soil liner (CSL). The risk of utilizing such a liner system is assessed relative to a regulatory compacted clay-based soil liner. The analytical solution developed is validated over a range of parameters against random field simulation using the Local Average Subdivision method, and the analytical solution is shown to be in good agreement with simulation. The analytical solution is then used to examine the “probability of exceedance” for a spatially variable GCL and CSL combined liner system. It is shown that the use of a GCL can potentially result in a low probability of exceedance when used with a spatially varying, high hydraulic conductivity CSL. The risk of exceedance generally decreases as the hydraulic conductivity of the CSL decreases. An example problem is presented to demonstrate the capabilities of the analytical solution.

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Towards a more rational approach to chemical compatibility testing of clay

Canadian Geotechnical Journal ◽

10.1139/t02-003 ◽

2002 ◽

Vol 39 (3) ◽

pp. 597-607 ◽

Cited By ~ 6

Author(s):

J K Kodikara ◽

F Rahman ◽

S L Barbour

Keyword(s):

Boundary Condition ◽

Hydraulic Conductivity ◽

Rigid Wall ◽

New Technique ◽

Rational Approach ◽

Lateral Strain ◽

Test Results ◽

Chemical Compatibility ◽

Test Technique ◽

Flexible Wall

Chemical compatibility tests using hydraulic conductivity testing with chemical permeants are normally undertaken to assess the integrity of compacted clayey liners used for waste containment. This paper highlights the fact that current routine methods of flexible wall and rigid wall testing techniques fail to represent the zero lateral strain boundary condition that is required to realistically represent the field situation. The test results indicate that flexible wall permeameters underestimate the likely increases in hydraulic conductivity due to chemicals, while the rigid wall permeameters can severely overestimate these effects. A new test technique, which incorporates the zero lateral strain condition in a simple manner, is presented. This technique involves the use of a rigid wall concept in a flexible wall permeameter. A split rigid mould is used to encase the soil specimen that is glued to the internal surfaces of the mould, to apply the zero lateral strain boundary condition. The new technique is shown to be suitable for both chemical compatibility and desiccation testing. The tests were undertaken with varying concentrations of saline water, methanol, and landfill leachate. The test results indicate that the new technique produces results that fall between the results obtained from flexible wall and rigid wall permeameters. It is argued that the new test technique provides a more rational approach for chemical compatibility testing than the current rigid wall and flexible wall techniques.Key words: soil, hydraulic conductivity, chemical compatibility, landfill, permeameter, boundary condition.

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Laboratory investigation of self-healing properties on geosynthetic clay liners with flaw

Archives of Environmental Protection ◽

10.1515/aep-2015-0007 ◽

2015 ◽

Vol 41 (1) ◽

pp. 53-58 ◽

Cited By ~ 1

Author(s):

Guang-Wei Zhang ◽

Hu-Yuan Zhang ◽

Jin-Fang Wang ◽

Lang Zhou ◽

Ping Liu ◽

...

Keyword(s):

Hydraulic Conductivity ◽

The Self ◽

Distilled Water ◽

Self Healing ◽

Test Results ◽

Geosynthetic Clay Liners ◽

Clay Liners ◽

Order Of Magnitude ◽

Flexible Wall ◽

Research Findings

Abstract The objective of this paper is to evaluate the self- healing properties of a commercially-available geosynthetic clay liner (GCL) using flexible-wall permeameter. The GCLs are produced by the same factory, but the contents of bentonite are different. Also the hydraulic conductivities (HC) of GCLs with no defect are different. In this study, specimens were completely saturated under the backpressure of 20 kPa before the test. Permeability tests were performed on GCL specimens with penetrating flaw and also on specimens permeated with distilled water and CaCl2 solutions. The test results were presented and discussed. Experimental results showed that the GCL with penetrating flaw did not exhibit complete self-healing in the case of flaw. After 120 days, the hydraulic conductivity increased by approximately an order of magnitude. In addition, CaCl2 solutions had a significant influence on the hydraulic conductivity. The research findings might be of interest to researchers and engineers who design liners for landfills and other liquid containment facilities

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The Influence of Compaction Effort in Laterite Soil with the Appearance of Sodium Bentonite as a Soil Liner

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.873.198 ◽

2017 ◽

Vol 873 ◽

pp. 198-202

Author(s):

Nor Azizah Che Azmi ◽

Mazidah Mukri ◽

Nur Aisyah Kasim ◽

Asmawati Che Hasan ◽

Nazri Nasir

Keyword(s):

Hydraulic Conductivity ◽

High Strength ◽

Environment And Public Health ◽

Health Issues ◽

Laterite Soil ◽

Sodium Bentonite ◽

Liner System ◽

Soil Liners ◽

Soil Liner ◽

Positive Results

Soil liner which is placed at the foundation of a landfill is very important in order to isolate waste materials and leachate from the environment. However, if not properly managed, the leachate can beriskytothe safety and serviceability of which are directly related to the environment and public health issues. Soil liners were proposed to minimize leachate egress and prevent ground pollution. In soil liner design, it is important to compact the layer properly in order to achieve low hydraulic conductivity and high strength of soil. In this study, different percentages of sodium bentonite were added to laterite soil to act as soil liner to stabilize the liner system. Sodium bentonite can easily absorb water more than a hundred percent of its weight. Thus, the sodium bentonites were chosen to be mixed with laterite soil. The differentpercentagesof sodium bentonite used are 5%, 10%, 15% and 20%. This research was carried out asan attempt to see the compaction effort for laterite soil mixedwith sodium bentonite. The outcomesof this study give positive results due to the potential of sodium bentonite to fulfill spaces in between soil particles. It is also found that sodium bentonite influences the resistance properties, hydraulic conductivity and the strength of soil.

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Characteristics of groundwater seepage with cut-off wall in gravel aquifer. II: Numerical analysis

Canadian Geotechnical Journal ◽

10.1139/cgj-2014-0289 ◽

2015 ◽

Vol 52 (10) ◽

pp. 1539-1549 ◽

Cited By ~ 71

Author(s):

Yong-Xia Wu ◽

Shui-Long Shen ◽

Zhen-Yu Yin ◽

Ye-Shuang Xu

Keyword(s):

Hydraulic Conductivity ◽

Soil Layer ◽

Ground Surface ◽

Surface Settlement ◽

Relative Depth ◽

Test Results ◽

Groundwater Seepage ◽

Ground Surface Settlement ◽

And Storage ◽

Selection Of

This paper presents a numerical investigation into the leakage behavior of cut-off walls in gravel strata due to dewatering in a deep excavation pit. The calculated values of the groundwater head and surface settlement using a model agree well with the measured values. Values of the hydraulic conductivity (k) and storage coefficient (Ss) of each soil layer are obtained from the test results when the cut-off wall is 43 m deep. The leakage through the cut-off wall in gravel is analyzed by considering a variation in hydraulic conductivity in different sections of the cut-off wall. The simulated results show that a significant leakage occurred in the 54 m deep cut-off wall. Although leakage did occur in the full cut-off wall in the confined aquifer, the full cut-off wall is still more efficient in preventing groundwater seepage than the partial cut-off wall. The relative depths of the cut-off wall and of the wells have a significant effect on ground surface settlement during the withdrawal of groundwater. Therefore, the appropriate selection of relative depth of both cut-off wall and pumping well is an effective way of controlling surface settlement outside the pit.

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Weathering-induced fissuring and hydraulic conductivity in a natural plastic clay

Canadian Geotechnical Journal ◽

10.1139/t98-068 ◽

1998 ◽

Vol 35 (6) ◽

pp. 1101-1108 ◽

Cited By ~ 12

Author(s):

K Yuen ◽

J Graham ◽

P Janzen

Keyword(s):

Hydraulic Conductivity ◽

Soil Aggregates ◽

Triaxial Tests ◽

Natural Clay ◽

Plastic Clay ◽

Order Of Magnitude ◽

Confining Pressures ◽

Flexible Wall ◽

High Plastic

Flexible-wall (triaxial) permeability tests have examined how laboratory-induced weathering affects the hydraulic conductivities of "undisturbed" specimens of a high-plastic expansive natural clay. After freezing-thawing or drying-wetting, hydraulic conductivities were on average about one order of magnitude higher than unweathered values. Reductions of hydraulic conductivity occurred in some specimens that were dried and then rewetted before permeation. The generally small changes in hydraulic conductivity are attributed to the expansive nature of the clay which allows swelling and reorientation of soil aggregates on thawing or rewetting. The changes may also have been influenced by the confining pressures of 35 kPa used in the tests. Hydraulic conductivities measured by oedometer were smaller than those in triaxial tests and varied strongly with pressure level.Key words: hydraulic conductivity, clay, plastic, weathering, desiccation, freezing.

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Transport of phenolic compounds through a compacted organoclay liner

Water Science & Technology ◽

10.2166/wst.1998.0125 ◽

1998 ◽

Vol 38 (2) ◽

pp. 143-150 ◽

Cited By ~ 3

Author(s):

Irene M. C. Lo ◽

Raymond K. M. Mak

Keyword(s):

Phenolic Compounds ◽

Hydraulic Conductivity ◽

Computer Program ◽

Silty Sand ◽

Natural Clay ◽

Liner Material ◽

Manufactured Products ◽

Organically Modified ◽

Soil Liner ◽

Hydrophobic Bonding

The transport of phenolic compounds through a compacted liner improved with organically modified bentonite (organoclay BB-40) was studied. Organoclay BB-40 is one of the manufactured products of Biomin International, Inc. and is modified with 40 lb of dicetyldimethylammonium per 100 lb of clay. The adsorption of phenolic compounds onto organoclay BB-40 is found to be significant, which could be attributed to the formation of hydrophobic bonding. The hydraulic conductivities of organoclay BB-40 are 1.98 × 10−7, 2.28 × 10−7 and 5.49 × 10−7 cm/sec for the phenol cell, 2-chlorophenol cell and 2,4,6-trichlorophenol cell, respectively. The experimental results of adsorption tests and hydraulic conductivity tests were input into the computer program “Pollute v9” to simulate the transport of phenolic compounds through a compacted organoclay liner material. The simulation result was then compared with phenol transport through the conventional soil liner (90% silty sand and 10% natural clay mineral). It indicates that the retardation of the transport of phenolic compounds using organoclay as a liner material is more significant than using the conventional soil liner, particularly for higher hydrophobic organics.

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Hydraulic conductivity of contaminated natural clay directly below a domestic landfill

Canadian Geotechnical Journal ◽

10.1139/t87-048 ◽

1987 ◽

Vol 24 (3) ◽

pp. 377-383 ◽

Cited By ~ 31

Author(s):

R. M. Quigley ◽

F. Fernandez ◽

E. Yanful ◽

T. Helgason ◽

A. Margaritis ◽

...

Keyword(s):

Hydraulic Conductivity ◽

Void Ratio ◽

Heavy Metal Concentration ◽

Natural Clay ◽

Domestic Waste ◽

Waste Landfill ◽

Copper Zinc ◽

Soluble Species ◽

Natural Clays ◽

Clay Barriers

The hydraulic conductivity of natural clays in the 1.5 m contamination zone below a 15 year old domestic waste landfill has been determined.Water-soluble contaminants such as chloride, sodium, and dissolved organic carbon have migrated about 1.0 m compared with only 15 cm for copper, zinc, iron, lead, and manganese. The migration, primarily by diffusion, has rendered the clay perfect for assessment of clay–leachate compatibility with respect to hydraulic conductivity, k.Oedometer tests on tube samples of the clay yielded k values of 1.4 × 10−8 cm/s with a slight decrease to about 1 × 10−8 cm/s in the upper 20 cm of clay at the waste–clay interface. Direct measurement of k on "undisturbed" tube samples, reconsolidated to their field stress state and permeated with pore fluid squeezed from adjacent contaminated samples, yielded values of 1.5 × 10−8 cm/s at 1 m depth decreasing to 0.75 × 10−8 cm/s at the interface.The decrease in k near the interface seems to correlate directly with increased pollutant concentration of soluble species, total heavy metal concentration, and a slight decrease in void ratio. The changes in k are so small, however, that for the test leachates and undisturbed test soils at this domestic waste site, it is concluded that the hydraulic conductivity has not changed significantly as a result of contamination. Key words: domestic waste, leachate, hydraulic conductivity, clay barriers, compatibility.

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