scholarly journals Effect of Fluid Chemistry on the Consolidation and Hydraulic Conductivity of Sand-Clay Liners

2021 ◽  
Vol 13 (20) ◽  
pp. 11213
Author(s):  
Muawia Dafalla
Keyword(s):  
Hydraulic Conductivity ◽  
Saline Water ◽  
Dry Weight ◽  
Coastal Zones ◽  
Clay Liners ◽  
Clay Liner ◽  
Fine Grained ◽  
Fluid Media ◽  
Liner Surface ◽  
Inorganic Chemical

The clay swelling potential of sand-clay liners exposed to saline water or specific chemicals can influence their hydraulic conductivity and other consolidation properties. The effect of saline water or chemicals on the sand-clay liners was thus studied and evaluated. The consolidation characteristics of the sand-clay liner can be different when tested under different fluid media. Bentonite and cement grouts are chemicals that have a significant effect on the sand-clay liners. Cement and bentonite can be used to seal off the openings within the liner to repair a defect or a malfunction. In this study, Al-Qatif clay was used to form a sand-clay liner when mixed with fine-grained sand (clay is 20% by dry weight). Soil samples extracted from this liner were exposed to inorganic chemical solutions. NaCl and CaCl2 solutions with concentration ranges of 0.1%, 0.5%, and 1.5% were used. Acidic water with pH values of 4, 5, and 6 was similarly used as fluid media. The effects of NaCl, CaCl2, and water with different acidity on the consolidation characteristics and hydraulic conductivity were obtained and compared to those of the distilled water. The effects of grout materials containing bentonite (1%, 2%, and 3% by weight) and cement (2.5%, 5%, and 7.5% by weight) were also investigated. The addition of bentonite grout to the liner surface was found to improve its hydraulic conductivity. The cement effect on the compressibility was found to be very significant. The findings of this study can serve as a guide for selecting parameters in the design and assessment of sand-clay liners in semi-arid regions and coastal zones.

Freeze–thaw cycling concurrent with cation exchange and the hydraulic conductivity of geosynthetic clay liners

2014 ◽  
Vol 51 (6) ◽  
pp. 591-598 ◽  
Author(s):  
Gregory P. Makusa ◽  
Sabrina L. Bradshaw ◽  
Erin Berns ◽  
Craig H. Benson ◽  
Sven Knutsson
Keyword(s):  
Hydraulic Conductivity ◽  
Cation Exchange ◽  
Pore Water ◽  
Geosynthetic Clay Liners ◽  
Clay Liners ◽  
Chemical Changes ◽  
Clay Liner ◽  
Freeze Thaw ◽  
Exchange Complex ◽  
Before And After

A study was conducted to assess the effect of cation exchange concurrent with freeze–thaw cycling on the hydraulic conductivity of a geosynthetic clay liner (GCL). GCLs were prehydrated by contact with silica flour moistened with synthetic subgrade pore water and subsequently permeated with a solution representing the pore water in the cover soil over a tailings facility. Control tests were conducted using the same procedure, except deionized (DI) water was used as the permeant liquid to preclude cation exchange from the permeant liquid. The GCLs were subjected to 1, 3, 5, 15, and 20 freeze–thaw cycles, and the hydraulic conductivity and exchange complex were determined before and after freeze–thaw cycling to assess chemical changes that occurred during freezing, thawing, and permeation. GCLs undergoing freeze–thaw cycling experienced little to no cation exchange through 5 freeze–thaw cycles. After 20 freeze–thaw cycles, 50% of the sodium (Na+) initially in the exchange complex was replaced by calcium (Ca2+). Dissolution of calcite within the bentonite is a likely source of the Ca2+. Hydraulic conductivity of the GCLs exposed to freeze–thaw cycling was lower than the hydraulic conductivity of a new GCL permeated with DI water (<2.2 × 10−11 m/s). A small increase in hydraulic conductivity (∼2.3 times), which may have been caused by cation exchange, occurred between 15 and 20 freeze–thaw cycles, but the hydraulic conductivity remained below the hydraulic conductivity of a new GCL unexposed to freeze–thaw cycling and permeated with DI water.

Statistical analyses of compacted clay landfill liners. Part 1: model development

1994 ◽  
Vol 21 (5) ◽  
pp. 872-882 ◽  
Author(s):  
Scott B. Donald ◽  
Edward A. McBean
Keyword(s):  
Hydraulic Conductivity ◽  
Geometric Mean ◽  
Model Development ◽  
Statistical Analyses ◽  
Compacted Clay ◽  
Clay Liners ◽  
Landfill Liner ◽  
Landfill Liners ◽  
Clay Liner ◽  
Spatial Correlation Structure

The acceptance of compacted clay liners, from a management point of view, has been a source of major concern because of the uncertainty associated with the hydrogeologic properties of the clay. By examining the flux of leachate through the compacted clay liner of a typical engineered landfill, where the hydraulic conductivity of the clay is represented by a stochastic process, an acceptance protocol suitable for compacted clay landfill liners is derived. Determination of the equivalent hydraulic conductivity of the clay liner is accomplished by comparing the flux of leachate through a homogeneous representation of the clay with the flux obtained by Monte Carlo analyses. Acceptance criteria are subsequently developed based on a statistical technique which calculates the confidence limits about a percentile of a probability distribution as well as about the mean of the distribution. For the landfill configuration simulated, the results indicate that the hydraulic conductivity of a compacted clay landfill liner follows a lognormal distribution and exhibits virtually no spatial correlation structure. In addition, for liners exhibiting a geometric mean conductivity of 10−7 cm/s and a standard deviation of 0.3, the geometric mean value is a conservative estimate of the hydraulic conductivity of the clay, provided the liner is constructed in a series of four 150 mm lifts. Key words: clay liners, hydraulic conductivity, statistical analyses, latin hypercube, equivalent hydraulic conductivity.

Heterogeneity detection in an experimental clay liner

2003 ◽  
Vol 40 (1) ◽  
pp. 149-160 ◽  
Author(s):  
Dominique Guyonnet ◽  
Jean-Christophe Gourry ◽  
Lucien Bertrand ◽  
Nadia Amraoui
Keyword(s):  
Hydraulic Conductivity ◽  
Geophysical Methods ◽  
The Other ◽  
Dipole Mode ◽  
Compacted Clay ◽  
Clay Liners ◽  
Hydraulic Test ◽  
Clay Liner ◽  
Other Hand

In situ hydraulic tests to characterize the field hydraulic conductivity of clay liners used in landfill applications are often positioned randomly. Yet it is well known that the field performance of low permeability clay liners is generally controlled by heterogeneities that may provide preferential pathways for flow. In this paper, an experimental clay liner is investigated in which heterogeneities were incorporated in a controlled fashion. Heterogeneities were embedded within a compacted clay liner at different locations in the plane and at different depths. Heterogeneities of composition were installed by excavating compacted clay at specific locations and replacing it with a more permeable material. Heterogeneities of compaction were introduced by loosely backfilling the clay into the excavations. Two geophysical methods, ground penetrating radar (GPR) and the EM-38 electromagnetic method, were used to examine whether anomalies detected by geophysics were or were not correlated with the precise locations of the heterogeneities. Hydraulic tests were used to characterize the permeability of the intact clay on the one hand and of the heterogeneities on the other hand. Three different in situ hydraulic test methods were used: a pulse test performed in a hand-augered borehole, a sealed single ring infiltrometer test, and a large scale infiltration test (4 m2) that uses a color tracer to detect possible preferential flowpaths. The GPR showed no significant correlation with heterogeneity locations, nor did the EM-38 method when used in the vertical dipole mode. The EM-38 method used in the horizontal dipole mode, showed significant correlation with heterogeneities when they were apparent at the surface. On the other hand, the method did not clearly detect heterogeneities located at depth. There was consistency between the values of hydraulic conductivity obtained from the different hydraulic field and laboratory tests. "Intact" clay hydraulic conductivities were found to lie between 10–10 and 4 × 10–9 m/s, while the hydraulic conductivity of the heterogeneities of composition was approximately 10–7 m/s. The results of this experiment suggest that the EM-38 method may be useful to optimize hydraulic test locations when characterizing clay liners for landfill applications.Key words: clay liner, hydraulic conductivity, heterogeneity.

Improvement of Barrier Soil Properties with Fly Ash to Minimize Desiccation Shrinkage

2012 ◽  
Vol 7 ◽  
pp. 1-11 ◽  
Author(s):  
Agapitus A. Amadi
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Water Content ◽  
Dry Weight ◽  
Shrinkage Strain ◽  
Volumetric Shrinkage ◽  
Unit Weight ◽  
British Standard ◽  
Fine Grained ◽  
Dry Unit Weight

Barrier Systems Built with Fine Grained Soils Frequently Loose their Hydraulic Integrity due to Desiccation Cracking either during Construction or Shortly Thereafter. Moreover, Typical Specifications for the Construction of Compacted Soil Liners and Covers Require that the Soil Be Compacted Wet of Optimum Water Contents to Achieve the Lowest Possible Hydraulic Conductivity, a Condition that Results in High Desiccation Shrinkage Values. however, such Soils Can Be Treated with Fly Ash to Maintain Low and Tolerable Desiccation Shrinkage Strains. in this Study, Volumetric Shrinkage Strains of Representative Fine Grained Soil Containing 0 – 20% Fly Ash by Dry Weight of Soil Compacted with the British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy, (BSH) Compaction Efforts at Moisture Contents Ranging from 10 – 20% Were Evaluated. Measurements Indicate that Volumetric Shrinkage Strain Decreased with Higher Fly Ash Content and that Fly Ash Effectively Reduced the Shrinkage of Untreated Soil Prepared Wet of Optimum from 4.4 – 7.7% to Values Well below the 4% Threshold. the Measured Shrinkage Strains Were Related to Water Content and Dry Unit Weight on the Dry Unit Weight – Moulding Water Content Curve in what Is Referred to as Acceptable Zone. Data Points within the Acceptable Zone Represent Test Results with Shrinkage Strain ≤ 4% which Ensures Compaction Efficiency. this Study Therefore Established that Fly Ash Application and Appropriate Regulation of the Moulding Water Content Are Feasible Means of Reducing the Risk of Barrier Soil Damage by Shrinkage Cracks while still Realizing Very Low Hydraulic Conductivity and Adequate Strength.

THE EFFECT OF SALINITY OF IRRIGATION WATER AND SPRAYING BY HUMIC ACID IN SOME OF MORPHOLOGICAL, PHYSIOLOGICAL PROPERTIES, GROWTH AND YIELD OF WHEAT (Triticum aestivum L.)

2020 ◽  
pp. 1-12
Author(s):  
E. K. Al-Fahdawe ◽  
A. A. Al-Sumaidaie ◽  
Y. K. Al-Hadithy
Keyword(s):  
Humic Acid ◽  
Plant Height ◽  
Irrigation Water ◽  
Saline Water ◽  
Block Design ◽  
Nitrogen Concentration ◽  
Dry Weight ◽  
Growth And Yield ◽  
Biological Yield ◽  
Phosphorus And Potassium

A pots experiment was conducted at the Department of Biology/College of Education for Girls/University of Anbar during Autumn season of 2018-2019 to study the effect of the salinity irrigation water and spray by humic acid in some of morphological, physiological, growth and yield traits of wheat cv. IPa. The experiment was randomized complete block design (RCBD) with three replications. The first factor was assigned for irrigation by saline water at four level (S0, S1, S2 and S3), while the second factor was the foliar spraying of humic acid in three level (0.0, 1.0 and 1.5 g l-1). The results showed that there was significant reduction in plant height, vegetative dry weight, biological yield and chlorophyll leaves content when the plants were irrigated by saline water approached to 41.09 cm, 0.747 g, 0.849 g plant-1 and 38.67 SPAD, respectively at salinity level of 8.3 ds m-1 compared with the plants which irrigated by fresh water. The total carbohydrates were significantly decreased at the treatment of 8.3 ds m-1 reached 18.71 mg g-1. Spray levels humic acid achieved a significant increase in plant height, dry weight of the vegetative part, biological yield and chlorophyll leaves content sprayed at 1.0 and 1.5 g l-1 compared to no sprayed. Nitrogen concentration was significantly increased, while both phosphorus and potassium were decreased in the vegetative parts of wheat as the salinity of irrigation water increased. However, the increase of humic acid levels led to significant increasing in nitrogen, phosphorus and potassium concentration.

Spatial Variability of Contaminant Transport in a Fractured Till, Avedøre Denmark

1999 ◽  
Vol 30 (4-5) ◽  
pp. 333-360 ◽  
Author(s):  
Larry McKay ◽  
Johnny Fredericia ◽  
Melissa Lenczewski ◽  
Jørn Morthorst ◽  
Knud Erik S. Klint
Keyword(s):  
Hydraulic Conductivity ◽  
Spatial Variability ◽  
Field Experiment ◽  
Contaminant Transport ◽  
Tracer Test ◽  
Conductivity Measurements ◽  
Fine Grained ◽  
Downward Migration ◽  
Rapid Transport ◽  
High Degree

A field experiment shows that rapid downward migration of solutes and microorganisms can occur in a fractured till. A solute tracer, chloride, and a bacteriophage tracer, PRD-1, were added to groundwater and allowed to infiltrate downwards over a 4 × 4 m area. Chloride was detected in horizontal filters at 2.0 m depth within 3-40 days of the start of the tracer test, and PRD-1 was detected in the same filters within 0.27 - 27 days. At 2.8 m depth chloride appeared in all the filters, but PRD-1 appeared in only about one-third of the filters. At 4.0 m depth chloride appeared in about one-third of the filters and trace amounts of PRD-1 were detected in only 2 of the 36 filters. Transport rates and peak tracer concentrations decreased with depth, but at each depth there was a high degree of variability. The transport data is generally consistent with expectations based on hydraulic conductivity measurements and on the observed density of fractures and biopores, both of which decrease with depth. Transport of chloride was apparently retarded by diffusion into the fine-grained matrix between fractures, but the rapid transport of PRD-1, with little dispersion, indicates that it was transported mainly through the fractures.

scholarly journals Hydraulic and Swell–Shrink Characteristics of Clay and Recycled Zeolite Mixtures for Liner Construction in Sustainable Waste Landfill

2021 ◽  
Vol 13 (13) ◽  
pp. 7301
Author(s):  
Marcin K. Widomski ◽  
Anna Musz-Pomorska ◽  
Wojciech Franus
Keyword(s):  
Hydraulic Conductivity ◽  
Exchange Capacity ◽  
Saturated Hydraulic Conductivity ◽  
Clay Soils ◽  
Compacted Clay ◽  
Clay Liner ◽  
Compacted Clay Liner ◽  
Drying And Rewetting ◽  
Swelling Characteristics ◽  
Shrinkage And Swelling

This paper presents research considering hydraulic as well as swelling and shrinkage characteristics of potential recycled fine particle materials for compacted clay liner for sustainable landfills. Five locally available clay soils mixed with 10% (by mass) of NaP1 recycled zeolite were tested. The performed analysis was based on determined plasticity, cation exchange capacity, coefficient of saturated hydraulic conductivity after compaction, several shrinkage and swelling characteristics as well as, finally, saturated hydraulic conductivity after three cycles of drying and rewetting of tested specimens and the reference samples. The obtained results showed that addition of zeolite to clay soils allowed reduction in their saturated hydraulic conductivity to meet the required threshold (≤1 × 10−9 m/s) of sealing capabilities for compacted clay liner. On the other hand, an increase in plasticity, swelling, and in several cases in shrinkage, of the clay–zeolite mixture was observed. Finally, none of the tested mixtures was able to sustain its sealing capabilities after three cycles of drying and rewetting. Thus, the studied clayey soils mixed with sustainable recycled zeolite were assessed as promising materials for compacted liner construction. However, the liner should be operated carefully to avoid extensive dissication and cracking.

Phytotoxic Effects of Treated Wastewater Used for Agricultural Irrigation On Root Hydraulic Conductivity and Plant Growth

2021 ◽  
Author(s):  
Sare Asli ◽  
Nedal Massalha ◽  
Muhamad Hugerat
Keyword(s):  
Cell Wall ◽  
Hydraulic Conductivity ◽  
Plant Growth ◽  
Root Elongation ◽  
Dry Weight ◽  
Cell Permeability ◽  
Treated Wastewater ◽  
Pressurized Water ◽  
Pore Sizes ◽  
Physical Effects

Abstract AimsTo determine the effects of treated wastewater (TWW) and dialyzed TWW (DTWW) through dialysis tube with a cut-off at 6000-8000 Da, on the water transport characteristics of maize seedlings (Zea mays L). MethodsLaboratory experiments were conducted to determine the effect of TWW on the hydraulic conductivity of excised roots. Moreover, the effect on transpiration, plant growth, root cell permeability and on the plant fresh and dry weight was determined. ResultsPressurized water flow through the excised primary roots was reduced by 25%-52%, within 90 min of exposure to TWW or DTWW. In hydroponics, DTWW affected root elongation severely by 58 %, while cell-wall pore sizes of same roots were little reduced (by 6%). Additionally, the exposure to TWW or DTWW caused inhibition of both leaf growth rate by (26%-70%) and transpiration by (14%-64%). While in soil growth, the plant fresh and dry weight was also significantly affected but not with secondary DTWW. Conclusions These impacts appeared simultaneously to involve phytotoxic and physical clogging impacts. First, the inhibition in hydraulic conductivity through live roots (phytotoxic and physical effects) after exposure to secondary DTWW was by 22%, while through killed roots accepted after hot alcohol disruption of cell membranes (physical effects only); was only by 14%. Second, although DTWW affected root elongation severely by 58%, cell-wall pore sizes of same roots were little reduced by 6%. We conclude that large molecules, such as polypeptides, remained after the dialysis process, may have produced hormone-like activity that affected root water permeability.

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