Electrokinetic Geosynthetics Research Articles

Improvements in vacuum-surcharge preloading combined with electro-osmotic consolidation on soft clayey soil with high water content

This study conducted laboratory tests on soft clayey soils to investigate the effectiveness of the combinations of vacuum-surcharge preloading and electro-osmotic treatment (EOC-VPM-SPM). To minimize the loss of vacuum pressure and mitigate clogging of the drainage system during the consolidation process, two improved methods were developed by optimizing technical characteristics and geometric layout of drainage boards. In the EOC-Alternate VPM-SPM method, alternate vacuum pressure was incorporated using two drainage boards with different lengths in the VPM system, combined with EOC to improve consolidation efficiency. In the multiple-electrodes EOC-VPM-SPM method, a new design of multiple drainage boards in a square tube layout fabricated through 3D printing was employed to provide efficient connections of the consolidation system. Furthermore, electrokinetic geosynthetics (EKG) was utilized as the cathode in the EOC system to minimize erosion and passivation of electrodes for the enhancement in consolidation efficiency. The properties of tested soils were analyzed to evaluate the feasibility of the improved methods. Test results indicated that the consolidation effects were significantly improved, with effectively mitigated clogging of the drainage system. Compared to the traditional method, the water content of the tested soil was reduced through the improved methods, resulting in increased uniformity of strength distribution.

Semi-analytical solution for one-dimensional coupling consolidation of original soil and electro-osmotic layer using horizontal electrodes

The application of horizontal electro-kinetic geosynthetics for electro-osmotic consolidation is becoming increasingly widespread. Such horizontal electrodes are typically arranged at intervals, allowing pore water in original soil to pass through the intervals and penetrate into the electro-osmotic layer. In this study, a one-dimensional semi-analytical solution for a double-layered electro-osmotic system incorporating the original soil was presented and verified. The effects of the soil properties on the consolidation process were investigated. Results revealed that original soil can achieve a significant consolidation effect, even better than electro-osmotic dredged soil. A smaller permeability coefficient of original soil significantly prolongs the consolidation time, while a thicker original soil can improve the average consolidation effect of the two layers. The proposed model provides new electrode arrangement ideas and theoretical support for horizontal electro-kinetic geosynthetics for electro-osmotic reinforcement.

Electroosmosis of gold tailings under multiple electrokinetic geosynthetics electrodes

In dry-stack tailing ponds with high fine-grained content, a high long-term saturation line can lead to dam failure. Electroosmotic consolidation is an effective method for reducing dam saturation lines. However, traditional electrodes have low corrosion resistance and poor contact, which limits the development of electroosmotic drainage technology for tailings. In this study, an electroosmotic drainage device, an electrokinetic geosynthetic (EKG) electrode, was designed. The influence law of the electrode material, potential gradient, and number of electrodes on the water drainage, current, and resistance was analyzed. The results show that the EKG electrode has excellent corrosion resistance, with its weight loss after electroosmosis, water drainage, and equivalent allowable current being 1.67%, 122%, and ∼2.3 times that of a copper electrode, respectively. Furthermore, it was found that the optimal potential gradient was 1.2 V/cm, and the water drainage cannot be improved by an exceedingly high potential gradient. The current pathway in the test box was in parallel, and the water drainage increased to 410% and the contact resistance decreased by 83% when the number of electrodes was four. These results and novel methodology provide new ideas for EKG electrode design and represent an effective method for saturation line control in gold tailing ponds.

Application and Parameter Optimization of Electro-Kinetic Geosynthetics Electrodes Based on the Wild Horse Optimizer in Horizontal Electric Field Sludge Dewatering

This study systematically compared the performance of five corrosion-resistant electrode materials for electro-dewatering. Through a comprehensive analysis of dewatering efficiency, energy consumption, and corrosion resistance, conductive plastic composite electrodes (EKG) were selected as the optimal electrode material for experimentation. Additionally, the impact of electric field strength and electrode spacing on the efficiency and energy consumption of electro-dewatering (EDW) was investigated. The results showed that the increase in electric field intensity could improve the solid content and dewatering efficiency of the sediments, but the corresponding energy consumption also increased. The increased spacing of the plates reduced the dehydration effect and increased the energy consumption. By employing the Wild Horse Optimization algorithm, empirical and multifactorial response models for the dewatering solidification process were established, aimed at predicting the dewatering performance and energy consumption. The study concludes that for the remediation of heavy metals, the electric field strength should not exceed 10 V/cm to avoid excessive heavy metal migration and potential adverse chemical reactions.

Dewatering and stabilization of Black cotton soil using Electrokinetic Geosynthetics

Electrokinetic Geosynthetics (EKG) is a platform technology used to dewater and stabilize highly saturated soft clayey soils, mine tailings, tunnelling slurry waste, sewage sludge etc. This laboratory study investigates the potential of EKG made of woven coir geotextile to stabilize highly expansive saturated black cotton soil collected from the Hubli-Dharward region of Karnataka state, India. An electoosmosis design was made in a tank setup where the soil was dewatered for a period of 7 days under three varying potential (15V, 30V & 60V) and different electrode configuration. The results demonstrated an increase in the rate of pore water dissipation by 500% at an optimum voltage gradient of 30V in various electrode spacing. The results of the EKG treatment at various voltages revealed that, as applied voltages increased up to 60 V, the liquid limits and plasticity indices rapidly dropped. An exponential increase in undrained shear strength of the soil was observed at an electrode configuration of 4A-1C.

Influence of organic and inorganic flocculants on sludge treated by electroosmotic vacuum preloading

The application of electrokinetic geosynthetics in electroosmotic vacuum preloading treatment of dredged sludge suffers the problems of severe clogging and uneven reinforcement effects. The effects of organic flocculant anionic polyacrylamide (APAM) and inorganic flocculant ferric chloride (FeCl3) on the electrical conductivity and permeability coefficient of dredged sludge were obtained in tests, and the optimal flocculant dosage was determined accordingly. A series of electroosmotic vacuum preloading model tests were performed by adding organic and inorganic flocculants to dredged sludge. Slight variations of the discharge rate and settlement amount were noticed between the sludge samples mixed with FeCl3 and APAM at the vacuum preloading stage, but after electroosmosis initiation, the discharge rate of the sludge with APAM became higher, as well as the final settlement. The shear strength and uniformity of sludge with APAM after treatment were better than those of sludge with FeCl3. Compared to FeCl3, electroosmotic vacuum preloading with APAM help increase the effective electric potential of sludge and benefit the discharging of heavy metals.

Shear Strength Performance of Electrokinetic Geosynthetics Treated Soft Clay after Water Immersion

The strength aspect of clay soil is a critical concern in practical engineering design. Electroosmosis (EO) has been adopted as a foundation treatment technology in some projects to increase the strength of soft clay. In order to widen the understanding on shear strength performance of EO-treated soil, the behavior of EO-treated soft clay using electrokinetic geosynthetics (EKG) as electrodes under the effect of water immersion was evaluated and compared with that of vacuum preloading (VP) treated soft clay under similar conditions. The main finding was that the EO-treated soil when immersed in water offered more resistance to the change in average water content than VP-treated soil. The average shear strength of EO-treated soil fell by 36.6% during 4 extra days of immersion. When the immersion time was extended to 10 days, the average shear strength fell by 65.4%. In contrast, the immersion time had little influence on the shear strength of VP-treated soil. Hence, if EO-treated soft clays are to be subjected to short-term water immersion, the shear strength of the treated foundations should be reappraised to ensure the safety of the engineering projects.

The assessment of innovative geotechnical slope repair techniques

Work to evaluate the effectiveness of innovative geotechnical slope repair techniques used on UK national highways is summarised. The techniques assessed were the planting of live willow poles, electrokinetic geosynthetics (EKG) and fibre-reinforced soil (FRS). These were used instead of conventional approaches to reduce the overall impacts of various challenges, including environmental constraints (habitat and visual) and access and utility constraints, and to reduce the scale and/or cost of traffic management and traffic delays. Trials have been undertaken over the last 20 years or so, but monitoring was generally limited to just a few years post-construction; longer term evaluation was not generally undertaken. The evaluated success – or otherwise – of the techniques led directly to recommendations for future use, ranging from the development of live willow pole design guidance and specification information, guidance on further EKG trials and cessation of the use of FRS, primarily on environmental grounds but also acknowledging the construction difficulties encountered. Life cycle analysis revealed that each technique provides significant carbon dioxide savings compared with rock fill replacement. More generic lessons learnt from the trials and the practical applications reported were used to produce guidance for future trials of innovative geotechnical repair techniques, including those for slopes.

Revealing underlying mechanisms affecting electrokinetic remediation of an artificially Cu- and Pb-contaminated loess using the external regulatory system with adsorbent

Considering extensive metallurgical mining activities in the northwest of China, handling Cu- and Pb-rich wastewater is a challenging task. Inappropriate handling of the Cu- and Pb-rich wastewater can lead to accumulation of Cu and Pb in the surrounding environment, thereby posing a serious threat to human health. Electrokinetic (EK) technology is an increasingly popular alternative to traditional approaches for contaminated soil remediation owing to its high effectiveness and low risk of secondary pollution. This study first proposed an external regulatory system with the adsorbent (ERSA) and investigated the effect of electrode type, ERSA, and cation exchange membrane (CEM) on the EK remediation of an artificially Cu- and Pb-contaminated loess. An EK reactor incorporating ERSA was applied to the EK experiments to circulate the electrolyte, not only making pH surrounding the cathode lower, but also preventing the formation of precipitation. The electrokinetic geosynthetics electrode released H+ and OH− faster and promoted their migration toward the specimen. However, because of the faster precipitation near the cathode, the boost in the remediation efficiency was hindered. Furthermore, considering the ERSA use, a decrease in soil pH near the cathode reduced the precipitation, thereby enhancing the EK remediation efficiency. In contrast, the use of CEM lowered the soil pH, increased the soil electrical conductivity (EC) and electric current, and aggravated the electroosmotic flow. The Cu remediation efficiency using the modified EK reactor was largely lifted to 85.52%, while the Pb remediation efficiency increased to 75.51%. These results shed light on an enhancement on the EK remediation efficiency and the potential of applying the modified EK reactor to remedy Cu- and Pb-rich water bodies.

Measurement methodology and characteristics of interfacial resistance in electro-osmosis

The electro-osmosis technique can be used for rapid dewatering and consolidation of deep soft foundations. Considering the abnormal volt-ampere characteristics of soil at the initial stage of electro-osmosis using electrokinetic geosynthetics (EKG) electrodes, the hypothesis that the interfacial resistance between electrode and soil is related to current was formulated. A new method was used to distinguish the soil resistance and interfacial resistance, and an experiment was designed to verify them. The results show that the soil resistance does not change with the changing current in the circuit, but the interfacial resistance is closely related to the current. The interfacial resistance decreases as the current increases and is approximately a power function of the current. This relationship applies to aluminium, copper, iron and EKG electrodes. In addition, a design for the field application of electro-osmosis was developed focusing on power supply and efficiency. The calculation results show that the proportion of soil effective potential is closely related to the potential gradient imposed by the power supply. The experimental results reveal the relationship between the potential gradient and the efficiency of electro-osmosis, which provides a theoretical basis for the determination and optimisation of electric power in electro-osmosis system design.

Electrokinetic geosynthetics restrained nitrogen release from sediment to overlying water through porewater drainage

Porewater is the primary carrier of sediment nitrogen and a crucial source of overlying water nitrogen; its separation thus is essential for restraining nitrogen release from sediment to overlying water. We developed a novel device using electrokinetic geosynthetics to drain porewater with nitrogen and restrain nitrogen release. A batch experiment lasted 1120 h (about 47 days) was conducted with 20 cm depth of overlying water under three conditions, i.e., undrained at 0 V/cm voltage gradient (control), drained at 0 V/cm, and drained at 0.5 V/cm. Under the pulsed direct current, once porewater drained, overlying water replenished sediment pore space and supplied porewater. Along with porewater drainage, sediment nitrogen concentration was reduced by 11%–30%, decreasing nitrogen release from sediment to overlying water from 83 mg/m2 in the first 100 h to −95 mg/m2 after about 600 h. Processes such as electroosmosis, electromigration, and redox reaction contributed to the restraint on nitrogen release. This research revealed the potentiality of applying electrokinetic geosynthetics to in-situ restraint on sediment nitrogen release in eutrophic waterbodies such as fishponds.

Consolidation of soft clay by cyclic and progressive electroosmosis using electrokinetic geosynthetics

Consolidation of soft clay by cyclic and progressive electroosmosis using electrokinetic geosynthetics

Vacuum Preloading Combined with Electroosmotic Dewatering of Dredger Fill Using the Vertical-Layered Power Technology of a Novel Tubular Electrokinetic Geosynthetics: Test and Numerical Simulation

Abstract A novel tubular EKG material in electroosmotic field test combined with a vacuum preloading method was first conducted in a reclamation project in Ningbo, China, by using a vertical-layere...

Large scale soft ground consolidation using electrokinetic geosynthetics

Field test of electro-osmotic consolidation with area of 800 square meters was carried out using electrokinetic geosynthetics (EKG). By introducing this field test, new concepts and solutions of difficulties in large scale application of electro-osmosis is introduced. Strategies of building smart DC power source to meet the large current intensity requirement of electro-osmosis are introduced. Roll polling program is a key program for the control system of smart DC power source. It reduces the requirement of current intensity to 1/3; it also decreases the energy consumption to less than 1 kW·h/m3. Design method for electro-osmotic consolidation is demonstrated while designing a field test. It is based on the energy level gradient theory. Design includes power estimation, wires and cables configuration, treatment time estimation and settlement estimation. The field test show that large scale application of electro-osmotic consolidation is feasible with acceptable power requirement and energy consumption. Electro-osmosis can accelerate consolidation and achieve better consolidation effect.

Performance comparison of different electrode materials for electro-osmosis treatment on subgrade soil

During the service life of subgrade, the moisture content increase on compacted subgrade soil can lead to bearing capacity serious degradation of the soil and exaggerated deformation. Electro-osmosis drainage is an effective method in reducing the moisture content of soil, which also serves to improve the subgrade. However, in practice, the low corrosion resistance and poor contact condition of conventional electrode materials make their energy inefficient. And the insufficient understanding of unsaturated soil electro-osmosis also limits the further application of this method. In this paper, a new type of electro kinetic geosynthetics (EKG) electrode was designed and used in electro-osmosis tests on unsaturated soil which was sampled from a reconstruction field in comparison with graphite and iron electrodes. The energy consumption, effective voltage variations, current variations and change in moisture contents under different voltage gradients were analyzed. A one-month field mesoscale test was conducted to verify the feasibility and efficiency of the new EKG electrode. Test results indicated that electro-osmosis drainage performed well with three kinds of electrode materials and the moisture reduction had reached 8.5–15.4%. The contact resistance of iron electrode would reach 1.8–4.1 times that of the EKG and graphite electrodes due to material corrosion. The newly-designed EKG electrode could reduce contact resistance by 19.7–40.8% for the layered fiber structure could enlarge the contact area between soil and electrodes.

Experimental investigation on expansive soils using electro kinetic geosynthetics (EKG) under cyclic loading

New applications for Geosynthetics have been identified if they can provide an active role, initiating biological, chemical or physical change to the matrix in which it is installed as well as providing the established functions. This can be achieved by combining the electro kinetic phenomena of electro osmosis, electrophoresis and associated electro kinetic functions such as electrolysis with the traditional functions of Geosynthetics. In this paper, a set of detailed experimental and software analysis is done on expansive soils (ie clay and block cotton soil) under various condition non saturated and fully saturated. Prototype of the cyclic loading disk (CLD) is designed, calibrated and installed. Soil samples are tested by using cyclic loading disk (CLD). For inducing Electro Kinetic Geosynthetics (EKG) effects and converting Alternate Current AC to Direct Current DC in soil samples, special electrical circuit is drafted from electrical CADD. Copper as Anode, Aluminium as Cathode and Perforated PVC tube as drain system. And Plaxis-3D software is used for analysis of soil in various conditions. As results and discussion obtained from the above made action, both expansive soils provides the good improvements from lateral sliding and shear strength parameters.

Impacts of electrokinetic isolation of phosphorus through pore water drainage on sediment phosphorus storage dynamics

Pore water is a crucial storage medium and a key source of sediment phosphorus. A novel equipment based on electrokinetic geosynthetics (EKGs) was used for isolating phosphorus from eutrophic lake sediments through pore water drainage. Three mutually independent indoor group experiments (A, B, and C) were conducted to investigate the effects of voltage gradient (0.00, 0.25, and 0.50 V/cm) on pore water drainage capacity, phosphorus removal performance, sediment physicochemical properties, and phosphorus storage dynamics. The average reduction in the sediment moisture and total phosphorus content was 2.5%, 4.3%, and 4.6% and 28.15, 75.95, and 112.65 mg/kg after 6 days of treatment for A, B and C, respectively. Efficient pore water drainage through gravity and electroosmotic flow and electromigration of phosphate were the main drivers of sediment-dissolved and mobilized phosphorus separation. A high voltage gradient facilitated the migration of pore water and the phosphorus in it. The maximal effluent total phosphorous (TP) concentration was up to 27.9 times that in the initial pore water samples, and negligible effluent TP was detected when the pore water pH was less than 2.5. The TP concentration was exponentially and linearly related to the pH and electronic conductivity of the electroosmotic flow, respectively. The migration of H+ within the sediment matrix promoted the liberation of metals bounded to phosphorus, particularly of Ca–P and Fe–P. Pore water drainage through an EKG resulted in Ex–P separation of up to 87.50% and a 13.84 mg/kg decrease in Ca–P and 125.35 mg/kg accumulation of low mobile Fe–P in the weak acid anode zone.

A comparative life cycle assessment of innovative highway slope repair techniques

Abstract The study evaluates the environmental performances of innovative and conventional remedial techniques to repair shallow highway slope failures. A comparative life cycle assessment (LCA) was performed, adopting a cradle-to-site system boundary, employing a cut-off approach for a hypothetical slope. Slope stabilisation systems under assessment include: granular rock fill replacement, planting live willow poles, fibre reinforced soil, and electrokinetic geosynthetics (or electro-osmosis). The functional unit of analysis was defined as the ability of each technique to initially stabilise 1 m2 of failed slope. Assessments explored the impacts of slope failures at two standard depths, and for a range of transport scenarios. Results (expressed in kgCO2e/m2 of failed slope) indicate that at both failure depths, across all transport scenarios, the greatest environmental impact was generated from the granular rock fill. The least impactful technique was willow pole planting, closely followed by electrokinetic geosynthetics. Relative to the granular rock fill replacement, the impact of the willow pole technique was about 7–8%, electrokinetic geosynthetics is 8–13% and the impact from fibre reinforced soil technique ranged from 19 to 32% of the control. In addition, the transportation of materials and equipment was the single largest contributor of carbon dioxide emissions.

Dewatering of Soft Marine Clays by using Electrokinetic Geosynthetics

Marine earth is found along the beach front areas of the world. This kind of dirt having uncommon properties like low shear quality and high compressibility. It was discovered that electrokinetic treatment is viable instrument in expanding the quality and expelling the pore water from mud. Electrokinetic geosynthetics (EKG) are recently created material which go about as terminals that readied by joining the electrokinetic marvels with elements of geosynthetics. The target of the work is to think about the dewatering effectiveness of EKG as cathode in marine dirt and the undrained shear quality. The different parameters contemplated are voltage(6V ,12V) and distinctive number of electrodes(1 anode and 2 anode with 10 cm spacing).The undrained shear quality of soil tests were considered when the treatment. The variety of current and opposition is additionally considered.

Laboratory tests of electro-osmotic consolidation combined with vacuum preloading on kaolinite using electrokinetic geosynthetics

Laboratory tests were conducted on kaolinite to investigate the effectiveness of electro-osmotic consolidation combined with vacuum preloading using electrokinetic geosynthetics (EKG). The results showed that the combined method could remove more water and induce larger surface ground settlements compared with the traditional vacuum preloading or electro-osmotic consolidation. Vacuum preloading was quite effective during the first 4 h, though the electro-osmotic consolidation took a main role in dewatering process after 9 h. The combined method could also hinder the development of cracks, induce higher negative pore water pressure and hence increase the efficiency of electro-osmotic consolidation. The results showed that deep electro-osmotic consolidation technique combined with vacuum preloading could result in significant water removal efficiency along with shorter electrode length. Furthermore, both electro-osmotic consolidation and the combined method could consolidate the soil efficiently with low energy consumption.