Electro-Osmotic Consolidation Studies on Peat and Clayey Silt Using Electric Vertical Drain

Abstract

Peat and soft soil deposits are abundant in Malaysia. Studies using electrokinetic geosynthetics (EKG) such as prefabricated electric vertical drains (EVD or ePVD) have shown the potential for the application of these materials in electrokinetic strengthening of soft clays and increasing solids content in mining tailings and sludges. There are no studies reported on the effectiveness of electro-osmosis using EVD in peat. Laboratory experiments were carried out to investigate the effectiveness of electroosmotic stabilization of two peat samples and a slightly organic clayey silt sample, from the North Sarawak region. Commercially available EVD was used to induce electro-osmosis and drainage of pore water. The influence of voltage gradient, organic content, initial water content, anode-cathode configuration and presence of roots on electro-osmotic consolidation was investigated. Electro-osmotic consolidation using EVDs was effective in the improvement of peat, over a large range of initial water contents. An increase in the voltage gradient generally improved consolidation. The maximum voltage gradient for optimum results appeared to be in the region 120 V/m. The 2anodes-1cathode configuration performed better than the 1anode-1cathode configuration. The presence of roots reduced the electro-osmosis effect.

A Review of Electrokinetic Treatment Technique for Improving the Engineering Characteristics of Low Permeable Problematic Soils

“…The first successful demonstration of the use of EK technique for soil remediation was performed in the Netherlands in 1986 and some other places in Europe and US for the removal of the toxic chemical species. These successful studies and applications encouraged some other researchers and in-situ studies, resulting in some breakthroughs in the understanding of EK phenomena to improve physical properties of low permeable soils for many approaches such as: improving stability of excavations and unstable embankments [18], [19], backfill strengthening and slope stabilization [18], [20], stabilization of soils by consolidation [21][22][23][24][25][26][27][28][29], soil drainage and ground water lowering [30], soil improvement stabilization of fine-grained soils [31][32][33][34][35][36][37][38], remediation of salt affected soils [1], dewatering of sludge [39][40][41], assisting pile driving [42][43][44][45] and treatment of dispersive soils [46], [47].…”

Electro-Osmotic Consolidation Experiments on an Organic Soil

“…A commercially available EVD was used to induce electro-osmosis and drainage of pore water. The parameters of the study namely, voltage gradient, initial water content and anode-cathode configuration were chosen based on the authors' study on peat samples from North Sarawak (Kaniraj et al 2010). The use of drainage tubes and pumping interval of drained water on electro-osmotic consolidation were investigated.…”

“…The electro-osmosis experiments were conducted on tests beds prepared in rectangular glass tanks of inner show the test tank used by the authors in their study on peats (Kaniraj et al 2010) which had 96% organic content compared to 49% organic content of the organic soil from Sibu. A hole in the two end walls, close to the floor of the test tank, facilitated the exit of drained water from the test bed and maintained the anode closed-cathode open condition.…”

“…While the water flowed out continuously when drainage took place at the bottom, in the experiments with vertical drainage tubes the drained water was pumped out at predetermined time intervals. A prefabricated band-shaped EVD used in the study on peats (Kaniraj et al 2010) was used as electrode. The EVD consisted of a conductive polyethylene core profiled with rows of ribs along its length and wrapped in a filter material.…”

“…However, there are no studies reported on the effectiveness of electro-osmosis in improvement of soft organic soils and peat. The authors carried out electro-osmotic consolidation studies on peat recently (Kaniraj et al 2010) in which the influence of voltage gradient, organic content, initial water content, anode-cathode configuration and presence of roots on electro-osmotic consolidation was investigated. This paper presents the details of the studies conducted on an organic soil.…”