Volume change and hydraulic conductivity properties of an expansive clay exposed to landfill leachate
- Authors: Jayasekera, Samudra
- Date: 2003
- Type: Text , Conference paper
- Relation: Paper presented at Problematic Soils 2003 Conference, Nottingham, UK : 28th July, 2003
- Full Text: false
- Reviewed:
- Description: E1
- Description: 2003000585
Stabilising volume change characteristics of expansive soils using electrokinetics : A laboratory based investigation
- Authors: Jayasekera, Samudra
- Date: 2007
- Type: Text , Conference paper
- Relation: Paper presented at Sri Lankan Geotechnical Society's First International Conference, Colombo, Sri Lanka : 5th-11th August 2007
- Full Text:
- Description: The objective of this project was to investigate the potential of electrokinetic treatment techniques to stabilise volume change characteristics of expansive soils. The investigations were carried out in the laboratory using locally collected expansive soils from three locations in central Victoria, Australia. A layer of soil was placed in glass tanks (900 mm x 350mm plan area) and compacted to a known density and water content typical of field conditions. Using electrodes inserted into the soil, a direct current was passed across the soil under different voltage gradients of 0.5, 1.0 and 2.0 V/cm for periods of 3, 5, 7, 10 and 14 days. After electrokinetic processing, soil were tested for volume change properties using soil reactivity indicators such as consistency limits, linear shrinkage, free swell index and shrink-swell index. The test results show that with electrokinetic treatments, the volume change potentials of the experimental soils reduced to a greater or lesser degree depending on the magnitude of the voltage gradient and processing time. Under certain voltage gradients and treatment durations, some experimental soils transformed from extremely reactive status to a slightly or almost non-reactive status. The experimental results suggest the potential of developing electrokinetic treatment technique to stabilise volume change properties of expansive soils effectively and efficiently.
- Description: 2003005481
An investigation into modification of the engineering properties of salt affected soils using electrokinetics
- Authors: Jayasekera, Samudra
- Date: 2008
- Type: Text , Thesis , PhD
- Full Text:
- Description: Soil salinity (due to ingress of excess amounts of dissolved salts in soil pores) and soil sodicity (due to excess amounts of sodium ions attached to the clay surface) are significant forms of land degradation in many parts of the world in particular in arid and semi arid regions. In Australia, soil salinity has long been identified as the major form of land degradation and the greatest environmental threat. Saline soils cover almost 6% of Australia’s land mass and impose severe threats on agricultural productivity and built infrastructure with an estimated annual loss of $250 million. In recent years, ‘soil sodicity’ is recognised as a far more significant form of land degradation and a severe environmental problem both in terms of affected land area and impact on the environment than is salinity as a problem in Australia. One third of Australian land mass is occupied by sodic soils costing an estimated $2 billion each year in lost production alone, with further significant impacts on the economy due to extensive damage to infrastructure facilities and the environment. [...]
- Description: Doctor of Philosophy
Improving engineering properties of soft clayey soils using electrokinetics : A laboratory based investigation
- Authors: Jayasekera, Samudra , Hall, Stephen
- Date: 2007
- Type: Text , Conference paper
- Relation: Proceedings of the 4th International Conference on Soft Soil Engineering - Soft Soil Engineering, Vancouver, BC p. 643-648
- Full Text: false
- Reviewed:
- Description: In this project, an in-situ soil treatment technique using electrokinetics was tested using laboratory experimental models in order to identify the potential of this approach to modify and improve the engineering properties of soft, low permeable clayey soils, with and without the introduction of a stabilising agent. Experiments were conducted in the laboratory using soils collected from soft alluvial soil deposit and basaltic soil deposit in central Victoria, Australia. A layer of soil was placed in glass tanks (900 mm x 350 mm plan area) and compacted to a known density and water content typical of field conditions. Using electrodes inserted into the soil, a direct current was passed across the soil under a voltage gradient of 0.5 V/cm for period of 14 days. In separate experiments, distilled water and a saturated lime solution were introduced to the soil via the anode electrode throughout the experimental duration with the aim of identifying the effectiveness of introduction of stabilising agents to soil using electrokinetics. After electrokinetic processing, soil specimens across the soil were tested for various engineering properties such as compressive strength, consistency limits, linear shrinkage, free swell index and compression index. From the results it was observed that the plasticity index of the soil decreased appreciably indicating increases in soil compressive strength and workability. Both the linear shrinkage and free swell index decreased by 70% without stabilising agents and by 90% with lime introduction, indicating the reduction in the potential for volumetric changes in the soils. With electrokinetic treatment alone, the unconfined compressive strength of the soils increased at least by 30% while in some locations the strength increase was in excess of 100% while the lime-enhanced electrokinetic treatment led to an almost 200% strength increase. The decrease in the compression index was between 10% and 15%. These results suggest the potential of developing this technique to improve the engineering properties of soft clayey soils more effectively and efficiently with or without the introduction of a stabilising agent. © 2007 Taylor & Francis Group.
Electro-osmotic and hydraulic flow rates through kaolinite and bentonite clays
- Authors: Jayasekera, Samudra
- Date: 2004
- Type: Text , Journal article
- Relation: Australian Geomechanics Vol. 39, no. 2 (2004), p. 79-86
- Full Text:
- Reviewed:
- Description: The objective of this paper is to discuss the effects of electrokinetics on the rate of flow of water through some low penneable clay soils. Experiments were carried out on test specimens prepared by compacting commerciully available kaolinite and sodium bentonite clays. Using falling head penneability tests, hydraulic conductivity values of these clay soils were determined. Subsequently, the experiments were repeated under different electric gradients to assess the effects of electrokinetics on the rate of flow. The flow characteristics were evaluated using the rate of electrooslllotic flow of water Q, (em'/s), coefficient of electroosmotic penneability k, (cm'lY/s), coetlicient of water transport etliciency k; (cm'/Amp/s). The test results suggest that the rate of flow of water through low penneable clay soils is significantly increased by some orders of magnitude due to the application of a direct current. This flow increase appears to be more pronounced for clays that have lower hydraulic conductivity values. It is noticed that electroosl1lotic penneability is independent ofclay type while the voltage gradienl has minimal effect on electroosmotic rate of flow for the tested clay soils.
- Description: C1
- Description: 2003000716
Some relationships between shrink-swell index, liquid limit, plasticity index, activity and free swell index
- Authors: Jayasekera, Samudra , Mohajerani, Abbas
- Date: 2003
- Type: Text , Journal article
- Relation: Australian Geomechanics Journal Vol. 38, no. 2 (2003), p. 53-58
- Full Text:
- Description: 2003000584
Effects of electrokinetic treatments on the properties of a salt affected soil
- Authors: Jayasekera, Samudra , Mewett, John , Hall, Stephen
- Date: 2004
- Type: Text , Journal article
- Relation: Australian Geomechanics Vol. 39, no. 4 (2004), p. 33-46
- Full Text:
- Reviewed:
- Description: This paper presents experimental results of a study undertaken to investigate the effects of electrokinetic treatments on selected chemical and physical properties of a salt contaminated (saline) soil. The study was conducted as a laboratory scale pilot project using locally available saline soil samples. The soil was subjected to an electric gradient by passing a direct current between inserted electrodes. After certain electrokinetic treatment periods, the properties of the soil were evaluated. The experimental data reveals that electrokinetic techniques could offer a low cost. rapid solution to treat saline soils. The removal efficiency of sodium ions was found to be greater than 90% within a relatively short time period of 14 to 30 days, using low current and voltage systems. After 14 to 30 days, the degree of salinity and sodicity decreased to a very low or negligible level. The unconfined compression strength of the soil increased by between 30 % to 100% in 30 days of electrokinetic treatment indicating the improvements in the physical properties, especially in the stress-strain characteristics of the soil. The liquid limit (LL) and plastic limit (PL) increased at the cathode.
- Description: C1
- Description: 2003000726
Modification of the properties of salt affected soils using electrochemical treatments
- Authors: Jayasekera, Samudra , Hall, Stephen
- Date: 2007
- Type: Text , Journal article
- Relation: Geotechnical and Geological Engineering Vol. 25, no. 1 (2007), p. 1-10
- Full Text:
- Reviewed:
- Description: In this project, an in situ soil treatment technique using the principles of electrokinetics was tested using laboratory experimental models in order to identify the potential of this approach in modifying and reinstating the physical properties of salt affected soils. Experiments were conducted in the laboratory using saline-sodic soils collected from two salt affected regions in central Victoria, Australia. Soil specimens were compacted in glass tanks to reproduce in situ density and in situ water content. Using mild steel electrodes inserted into the soil, a direct current was passed through the soil under a constant potential gradient of 0.5 V/cm for a period of 14 days. In separate experiments, distilled water and a saturated lime solution were introduced to the soil via the anode over this experimental period. It was observed that the soil dispersion, otherwise known as soil sodicity (measured as ESP - Exchangeable Sodium Percentage and SAR - Sodium Absorption Ratio) decreased by up to 90% in most regions of the soil between the electrodes. The compressive strength of the soil increased in excess of 100% with electrokinetic treatment alone while the lime-enhanced electrokinetic treatment led to an almost 200% strength increase. The liquid limit and plastic limit of the soil increased causing the plasticity index to decrease, indicating increases in soil compressive strength and workability. These results indicate the potential of this technique for improving the physical properties of salt affected soils both effectively and efficiently, and in particular gives hope for the remediation of salt affected land for infrastructure management and development. © Springer Science+Business Media, Inc. 2006.
- Description: C1
- Description: 2003004772
Long-term strength and bearing capacity characteristics of a basal clay soil subjected to landfill leachate
- Authors: Jayasekera, Samudra
- Date: 2002
- Type: Text , Conference paper
- Relation: Paper presented at the International workshop on environmental geomechanics 2002, Ascona, Switzerland : 28th June, 2002
- Full Text: false
- Reviewed:
- Description: E1
- Description: 2003000174
A study of effects of municipal landfill leachate on a basaltic clay soil
- Authors: Jayasekera, Samudra , Mohajerani, Abbas
- Date: 2001
- Type: Text , Journal article
- Relation: Australian Geomechanics Journal Vol. 36, no. 3 (2001), p.
- Full Text:
- Description: The performance of a landfill clay liner is generally evaluated using the hydraulic conductivity values obtained from laboratory tests during the design stage. Laboratory tests for the determination of hydraulic conductivity are frequently carried out either using water as the permeating liquid or some times using a chemical permeant to represent leachate. However, any investigations incorporating time as a variable in analysing the effects of leachate on various other soil properties that can influence the hydraulic conductivity are very limited. This study is aimed at investigating the effects of landfill leachate on the performance of a compacted basaltic clay soil, over a period of time. For this purpose, a typical Melbourne basaltic clay with varying percentages of montmorillonite clay was selected and a synthetic leachate was developed based on the composition of typical municipal waste landfill leachate reported in the literature. The clay -leachate interactions were allowed take place under controlled anaerobic laboratory conditions. Samples were then tested at different time periods to identify possible variations of engineering properties such as volume change, consistency and grain size distribution due to the effect ofleachate over time, since variation of these soil properties can affect the hydraulic conductivity of a clay soil. The analysis of test results suggests that the behaviour of a basaltic clay liner could be significantly affected by clay leachate interactions over time, due to possible alterations to physical and mineralogical properties of the clay.
- Description: 2003004211
Electrokinetics to deal with salinity impacts on urban and rural infrastructure : A laboratory based investigation
- Authors: Jayasekera, Samudra
- Date: 2005
- Type: Text , Conference paper
- Relation: Paper presented at Women in Research (WiR) ‘Women Doing Research’ 2005 conference, Gladstone, Canada : November, 2005
- Full Text: false
- Description: In this project, an in-situ soil treatment technique based on electrokinetics was tested in order to identify the potential of this approach to modify the engineering properties of salt affected soils.
- Description: E1
- Description: 2003001097
An investigation of long term effects of leachate on landfill clay liners
- Authors: Jayasekera, Samudra , Mohajerani, Abbas
- Date: 2001
- Type: Text , Conference paper
- Relation: Paper presented at 3rd Conference on Developments in Victorian Geology and Mineralisation, Newcastle, NSW : 28th-30th of November 2001
- Full Text: false
- Description: 2003004214
Electrokinetics to modify strength characteristics of soft clayey soils : A laboratory based investigation
- Authors: Jayasekera, Samudra
- Date: 2015
- Type: Text , Journal article
- Relation: Electrochimica Acta Vol. 181, no. (2015), p. 39-47
- Full Text: false
- Reviewed:
- Description: The effects of Electrokinetic (EK) processing on compressive strength characteristics of two types of soils were investigated using laboratory experimental models. Soils were collected from soft alluvial soil deposit (Soil S1) and basaltic soil deposit (Soil S2) in central Victoria, Australia. A layer of soil was placed in glass tanks (90 cm × 18 cm plan area) and compacted to a known density and water content typical of field conditions. Using electrodes inserted into the soil, a direct current was passed across the soil under various voltage gradients (0.5, 1.0, 2.0 V/cm) for periods of 7, 14, 30 and 60 days. Throughout the experimental duration, test samples were supplied with a continuous flow of water via the hollow core anode from external reservoirs. Unconfined compression (UC) tests were conducted on original (untreated) soils and EK processed soils. From the test results it is noted that, soil compressive strength increases with the increasing processing time and increasing voltage gradients, at various rates. Under certain voltage gradients and processing times, around 175% and 200% strength increases are observed. In general, stress increases of at least 30% or more are reported for both soils under all test conditions. It is apparent that the variation in strength can be attributed to several complex and interrelated processes that become active under EK processing. These may include, (i) Electroosmotic advection - When a soil is subjected to EK processing with an open electrode configuration, the water content of the soil varies predominantly due to the electroosmotic advection while natural drying and evaporation could also add to the decrease in water content to some extent, depending on the time and environmental conditions such as temperature and humidity. The test results show that with the decrease in water content, there is a corresponding increase in the strength. (ii) Electromigration - The electromigration of charged ions and their interaction with clay minerals can also affect the soil strength due to the variations in the DDL (Diffused Double Layer) ionic concentration and subsequent modifications in the soil structure. (iii) Ionic Diffusion and Aging - After the complete termination of EK processes, the ionic concentrations still continued to modify at a slower rate. This is considered to be due to the ionic diffusion. In this phase too, cementation bonds may continue to develop that could contribute to the increase in soil strength. During this period, two other processes, i.e. natural drying of soil and aging may continue that can also affect the variation of soil strength. © 2015 Elsevier Ltd. All rights reserved.
Towards sustainable design of landfill clay liners: A Case study
- Authors: Jayasekera, Samudra
- Date: 2016
- Type: Text , Book chapter
- Relation: Sustainability in the Mineral and Energy Sectors Chapter 19 p. 329-343
- Full Text: false
- Reviewed:
- Description: The design and maintenance of landfills for waste disposal has received great attention over the last few decades dues to the increasing and attention paid to environment protection issues, such as ground and ground water protection. Over the years , landfill liner construction has seen innovative new practices such as addition of engineered clays, synthetic lining and designing of more sophisticated leachate collection systems. The main objective of such pratices is to enhance the landfill liner performance as a hyrdraulic barrier system and to minimise or prevent the migration of landfill leachate into the surroundinng hydro-geological system. The compacted c;lay liners (CCLs) are among the most widely used hydraulic barrier system in modern waste containment. "From abstract"