EFFECT OF ELECTRO OSMOTIC TECHINQUE IN CONSOLIDATION OF SOIL full report
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08-02-2010, 07:25 AM
EFFECT OF ELECTRO OSMOTIC TECHINQUE IN CONSOLIDATION OF SOIL
Electro osmotic consolidation means the consolidation of soft clays by the
application of electric current.
It was studied and applied for the first time by Casagrande.
It is inherent that fine grained clay particles with large interfacial surface will
consolidate and generate significant settlement when loaded.
The settlement creates problem in the foundation engineering.
Electro osmosis was originally developed as a means of dewatering fine grained soils
for the consolidation and strengthening of soft saturated clayey soils.
Electro osmotic dewatering essentially involves applying a small electric potential
across the sediment layer.
It is the process where in positively charged ions move from anode to cathode.
ie. Water moves from anode to cathode where it can be collected
out of soil
Electro osmotic flow depends on soil nature, water content, pH and on ionic type
concentration in the pore water.
ELECTRO OSMOTIC CONSOLIDATION
Due to the applied electric potential the electrolysis of water occurs at the
2H2O -> O2 (g) + 4H+ +4e- oxidation (anode)
4H2O + 4e- -> 2H2 (g) + 4OH- reduction (cathode)
The clay particles have a â€œve charge. These â€œve charge produce an electro static
surface property known as the double layer which creates a net abundance of cations
in pore space.
Electro osmotic transfer of water through a clay is a result of diffuse double layer
cations in the clay pores being attracted to a negatively charged electrode or
When electrodes are placed across a saturated clay mass and direct current is applied
,water in the clay pore space is transported towards cathode by electro osmosis.
In addition frictional drag is created by the motion of ions as they move through the
clay pores helping to transport additional water.
The flow generated by the electric gradient is called electro osmotic flow.
EVALUATION OF ELECTRO OSMOTIC CONSOLIDATION
Determination of parameters
Electrical operation systems for field application
Spacing between electrodes
Cost of electrodes and installation cost
CASE STUDY 1 ELECTRO OSMOTIC DEWATERING OF DREDGED
SEDIMENTS :- BENCH SACLE INVESTIGATION AT INDIANA HARBOUR (USA)
The Indiana Harbour has not been dredged for over 20 years due to lack of an
acceptable disposal site
It resulting in the accumulation of large amount of highly contaminated sediments
The main problem with the disposal of sediment to the CDP was slow consolidation of
sediment due to its very high water content.
This study investigated the feasibility of using an electro osmotic dewatering
technology to accelerate dewatering and consolidation of the sediment there by
allowing more rapid disposal of sediment in to the CDP.
MATERIAL (SOIL SAMPLE)
Samples were obtained by dredging from the Indiana Harbour.The
sediments were tested for water content, optimum moisture content and pH
CASE STUDY 2EFFECT OF USING ELECTRO CONDUCTIVE PVD IN THE CONSOLIDATION OF RECONSTITUTED ARIAKE CLAY
The deposits of Ariake clay consolidate generate significant settlement when loaded
which causes problems in foundation engineering.
The low permeability of clay results in longer duration to achieve primary
To shorten the consolidation time vertical drains are installed to shorten the
The induced consolidation of reconstituted Ariake clay was conducted using electro
conductive PVD as electrodes and the results were compared with an ordinary PVD
MATERIAL (SOIL SAMPLE)
The soil sample used was leached marine Ariake clay collected at Saga
Plain in Saga Japan. The sample excavated at about 2m depth was generally a very soft
gray silty clay (about 66% clay, 26% silt, 8% fine sand) with natural water content
of about 110% â€œ 120%
The consolidation period can be reduced by electro osmotic consolidation technique.
The process is very efficient in low permeability clays in which the electro osmotic
permeability is greater than the hydraulic permeability.
Electro osmotic permeability was 200 to 1000 times greater than the hydraulic
This method is suitable for local application on small volumes or for impermeable
After treatment water content decreases and shear strength increases and it was more
than what was expected just from dewatering.
The pH of soil will increase to as high as 11 or 12 at the cathode and decrease to
almost 2 at the cathode.
Metal anodes will corrode.
The applied voltage and electric current generates heating.
The heating effect increases power consumption.
Dewatering of sediment can be enhanced by the electro osmosis induced by the
application of an electric potential
Incorporating electro kinetic item in the properties of PVD is very useful in
dewatering highly compressible and low permeability clay
Faster rate of settlement was achieved using electro conductive drains
Significant rate of increase in strength of EO-treated soils was achieved as a
consequence of decrease in water content formation of menisci in the soil voids and
bonding of soil particles by insoluble chemical precipitates as a result of the
complex chemical reactions generated and ion re-exchange which altered the plasticity
Application of electric potential will result in energy consumption.
Thinking To Register
25-01-2013, 04:25 PM
iam going to take a seminar and presentation about this topic ...can i get full seminar and presentation reprt of about 40 pages ...pls help