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

1998 ◽  
Vol 35 (6) ◽  
pp. 1101-1108 ◽  
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.

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

2015 ◽  
Vol 41 (1) ◽  
pp. 53-58 ◽  
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

Consolidation and Hydraulic Conductivity of High-Plastic Clay Reinforced with Waste Tire Fibers

2020 ◽  
Vol 49 (6) ◽  
pp. 20200079
Author(s):  
Mohit K. Mistry ◽  
Shruti J. Shukla ◽  
Chandresh H. Solanki ◽  
Sanjay Kumar Shukla
Keyword(s):  
Hydraulic Conductivity ◽  
Plastic Clay ◽  
Waste Tire ◽  
High Plastic

scholarly journals SHMP-Amended Ca-Bentonite/Sand Backfill Barrier for Containment of Lead Contamination in Groundwater

2020 ◽  
Vol 17 (1) ◽  
pp. 370 ◽  
Author(s):  
Yu-Ling Yang ◽  
Krishna R. Reddy ◽  
Wen-Jie Zhang ◽  
Ri-Dong Fan ◽  
Yan-Jun Du
Keyword(s):  
Hydraulic Conductivity ◽  
Tap Water ◽  
Lead Contamination ◽  
Retardation Factor ◽  
Cutoff Wall ◽  
Order Of Magnitude ◽  
Slurry Trench ◽  
Slurry Wall ◽  
Flexible Wall ◽  
Favorable Conditions

This study investigated the feasibility of using sodium hexametaphosphate (SHMP)- amended calcium (Ca) bentonite in backfills for slurry trench cutoff walls for the containment of lead (Pb) contamination in groundwater. Backfills composed of 80 wt% sand and 20 wt% either Ca-bentonite or SHMP-amended Ca-bentonite were tested for hydraulic conductivity and sorption properties by conducting laboratory flexible-wall hydraulic conductivity tests and batch isothermal sorption experiments, respectively. The results showed that the SHMP amendment causes a one order of magnitude decrease in hydraulic conductivity of the backfill using tap water (1.9 to 3.0 × 10−10 m/s). Testing using 1000 mg/L Pb solution resulted insignificant variation in hydraulic conductivity of the amended backfill. Moreover, SHMP-amendment induced favorable conditions for increased sorption capacity of the backfill, with 1.5 times higher retardation factor relative to the unamended backfill. The Pb transport modeling through an hypothetical 1-m-thick slurry wall composed of amended backfill revealed 12 to 24 times of longer breakthrough time for Pb migration as compared to results obtained for the same thickness slurry wall with unamended backfill, which is attributed to decrease in seepage velocity combined with increase in retardation factor of the backfill with SHMP amendment. Overall, SHMP is shown to be a promising Ca-bentontie modifier for use in backfill for slurry trench cutoff wall for effective containment of Pb-contaminated groundwater.

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

2011 ◽  
Vol 194-196 ◽  
pp. 909-912 ◽  
Author(s):  
Si Fa Xu ◽  
Zhe Wang ◽  
Yong Zhang
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Layer ◽  
Low Permeability ◽  
Test Results ◽  
Natural Clay ◽  
Compacted Soil ◽  
Waste Landfill ◽  
Liner System ◽  
Flexible Wall ◽  
Soil Liner

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.

scholarly journals Effect of Confining Conditions on the Hydraulic Conductivity Behavior of Fiber-Reinforced Lime Blended Semiarid Soil

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3120
Author(s):  
Abdullah Ali Shaker ◽  
Mosleh Ali Al-Shamrani ◽  
Arif Ali Baig Moghal ◽  
Kopparthi Venkata Vydehi
Keyword(s):  
Hydraulic Conductivity ◽  
Expansive Soils ◽  
Dry Weight ◽  
Rigid Wall ◽  
Saturated Hydraulic Conductivity ◽  
Morphological Properties ◽  
Expansive Clay ◽  
Confining Pressures ◽  
Flexible Wall ◽  
Fiber Materials

The hydraulic properties of expansive soils are affected due to the formation of visible cracks in the dry state. Chemical stabilization coupled with fiber reinforcement is often considered an effective strategy to improve the geotechnical performance of such soils. In this study, hydraulic conductivity tests have been conducted on expansive clay using two different types of fibers (fiber cast (FC) and fiber mesh (FM)) exhibiting different surface morphological properties. The fiber parameters include their dosage (added at 0.2% to 0.6% by dry weight of soil) and length (6 and 12 mm). Commercially available lime is added to ensure proper bonding between clay particles and fiber materials, and its dosage was fixed at 6% (by dry weight of the soil). Saturated hydraulic conductivity tests were conducted relying on a flexible wall permeameter on lime-treated fiber-blended soil specimens cured for 7 and 28 days. The confining pressures were varied from 50 to 400 kPa, and the saturated hydraulic conductivity values (ksat) were determined. For FC fibers, an increase in fiber dosage caused ksat values to increase by 9.5% and 94.3% for the 6 and 12 mm lengths, respectively, at all confining pressures and curing periods. For FM fibers, ksat values for samples mixed with 6 mm fiber increased by 12 and 99.2% for 6 and 12 mm lengths, respectively for all confining pressures at the end of the 28-day curing period. The results obtained from a flexible wall permeameter (FWP) were compared with those of a rigid wall permeameter (RWP) available in the literature, and the fundamental mechanism responsible for such variations is explained.

Estimation and Scaling of the Near-Saturated Hydraulic Conductivity

1999 ◽  
Vol 30 (3) ◽  
pp. 177-190 ◽  
Author(s):  
Per Atle Olsen
Keyword(s):  
Hydraulic Conductivity ◽  
Saturated Hydraulic Conductivity ◽  
Scaling Analysis ◽  
Laboratory Measurements ◽  
Estimation Errors ◽  
Geometric Means ◽  
Top Soil ◽  
Structured Soils ◽  
Order Of Magnitude

The hydraulic conductivity in structured soils is known to increase drastically when approaching saturation. Tension infiltration allows in situ infiltration of water at predetermined matric potentials, thus allowing exploration of the hydraulic properties near saturation. In this study, the near saturated (ψ≥-0.15 m) hydraulic conductivity was estimated both in the top- and sub-soil of three Norwegian soils. A priory analysis of estimation errors due to measurement uncertainties was conducted. In order to facilitate the comparison between soils and depths, scaling analysis was applied. It was found that the increase in hydraulic conductivity with increasing matric potentials (increasing water content) was steeper in the sub-soil than in the top-soil. The estimated field saturated hydraulic conductivity was compared with laboratory measurements of the saturated hydraulic conductivity. The geometric means of the laboratory measurements was in the same order of magnitude as the field estimates. The variability of the field estimates of the hydraulic conductivity from one of the soils was also assessed. The variability of the field estimates was generally smaller than the laboratory measurements of the saturated hydraulic conductivity.

Towards a more rational approach to chemical compatibility testing of clay

2002 ◽  
Vol 39 (3) ◽  
pp. 597-607 ◽  
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.

scholarly journals A Case Study On Predicting The Environmental Impacts Of Untreated Effluent Generated From Tannery Industrial Estate In Dhaka, Bangladesh

2020 ◽  
Vol 13 (3) ◽  
pp. 22-31
Author(s):  
Shakil A. Masum ◽  
Md. Sultanul Islam
Keyword(s):  
Environmental Impact ◽  
Discharge Rate ◽  
Soil Aggregates ◽  
Elevated Concentration ◽  
Natural Ecosystem ◽  
Industrial Site ◽  
Discharge Rates ◽  
Regulatory Standard ◽  
Order Of Magnitude ◽  
Recommended Guidelines

Significant amounts of heavy metals in the directly discharged wastewater released from the newly built tannery industrial site in Dhaka, Bangladesh are reported. Despite their detrimental impacts on public health and natural ecosystem, no environmental impact study is yet conducted. Therefore, information on safe discharge rates are not available. In this study, the extent of pollution around the industrial site is investigated for four representative trace metals. Temporal and spatial distributions of chromium (Cr), lead (Pb), cadmium (Cd) and arsenic (As) have been predicted using a numerical model with the aim to estimate safe discharge of these metal contaminants. From multiple simulation runs it has been estimated that a discharge of0.026 m3 of wastewater per day can lead to high levels of Cr and Pb accumulation, exceeding the regulatory standard limits, in the study area. Whilst As and Cd concentrations remain below the advised limits in most cases at this rate. However, an order of magnitude reduction in the total discharge rate, i.e.,0.0026 m3 per day, results into the metal accumulation below the recommended guidelines in all cases. Elevated concentration of Pb is found to be limited to the top 0.5 m of the soil as compared to Cr, As and Cd, which exhibit larger spread along the depth of the soil. The relative dominance of the metal contamination follows the sequence: Pb>Cr>As>Cd as sorbed concentration in soil aggregates and Cr>Pb>As>Cd as aqueous concentration in soil porewater. Further investigations that are essential for a comprehensive environmental impact assessment have been highlighted.

scholarly journals INFLUENC OF IRRIGATION PERIODS AND ORGANIC FERTILIZER ON SOIL PHYSICAL CHARACTERIZATION UNDER THE SYSTEM OF RICE INTENSIFICATION (SRI)

2017 ◽  
Vol 48 (3) ◽  
Author(s):  
Al-Hasanie & Al-Maadhedi
Keyword(s):  
Hydraulic Conductivity ◽  
Average Rate ◽  
Day Treatment ◽  
Soil Aggregates ◽  
Organic Fertilizer ◽  
Irrigation Schedule ◽  
System Of Rice Intensification ◽  
Research Station ◽  
Irrigation Interval ◽  
Rice Intensification

A field trial was conducted at Al-Mishkhab Rice Research Station at Najaf province during 2015 rice season to assess the effects of irrigation periods and organic manure on soil physical properties under System of Rice Intensification The experiment was conducted using split   split plot arrangement with RCBD design with three replicates. The main plots were irrigation schedule where practiced: daily and intermittent water application where irrigation water was at two different intervals 3, 5 day. The sub plots were varieties (anber33,jasmin) and three amount of organic manures 0, 5, 10 ton.haˉ¹, planted under System of Rice Intensification (SRI) compared with conventional method. The results indicated that superiority of irrigation interval 3 day treatment with 10 ton.haˉ¹ In the attribute of soil density and total soil porosity, as this treatment gave the  average in the bulk density 1.24 Mg m-3  compare with fertilization treatment with irrigation 3 days intervals, which gave an average of less than 1.39 Mg m-3, as well as the treatment excelled in the  total porosity of the soil as it gave the highest average 50.18 %, while the comparison gave the lowest percentage of soil aggregate reached 13.00 %. In irrigation 3 days interval and 10 ton.haˉ¹ of organic matter led to increased values of available water to 0.331 cm3.cm -3 compared with a sample before planting, which gave an average of less than 0.193 cm3.cm-3. Given the treatment of interaction between the irrigation 3 days intervals and fertilization treatment recorded the lowest average porosity 48.13 %. The high percentage of soil aggregates, was with the treatment irrigation 3 days interval on the highest average rate of 57.00 % compared with the comparison treatment fertilization and daily irrigation, which 10 ton.haˉ¹ quantities highest average for the hydraulic conductivity reached 0.1320 cm . min-1 compared with the treatment of fertilizing comparison and irrigation daily which gave the lowest average saturated hydraulic conductivity reached 0.0577 cm . min-1.

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