CONTENTS:

o Introduction

o What is electro kinetic geo synthetics?

o Principle

o Applications

o Slope stabilization

o Case study

o Conclusion

INTRODUCTION:

o Geo synthetics are used in civil engineering to

carry out a range of functions.

o All of these functions are limited by the rate at

which water is able to flow.

o New applications for geo-synthetics provide

an active role in established functions.

Electro kinetic geo synthetics

o Electro kinetic geo synthetics (EKG)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 geo synthetics

of drainage, filtration, containment and

reinforcement.

PRINCIPLES OF ELECTRO KINETICS

Electro osmosis: water transport from anode to cathode

APPLICATIONS:

o Strengthening of slopes and cuttings.

o Electro kinetic consolidation.

o Dewatering of sewage sludge.

o Dewatering and recovery of water from

mine tailings.

EKG FILTER BAG&EK DRAINAGE BAG

EKG electrodes for slurries/sludge dewatering and cutting/slope stabilization.

EKG electrodes for planar conditioning in sports turf/agriculture applications.

SLOPE STABILIZATION

The concept of EKG strengthening

of a slope is based on :

oThe orientation of the electrodes

is selected to intercept any

potential failure plane.

oElectro-osmotic treatment results

in an immediate reduction in pore

water pressure and accelerated

dewatering of the slope which

results in an increase in the shear

strength of the soil, reducing the

risk of a slip plane developing.

Concept of Electro-osmotic

consolidation.

CASE STUDY:

Electro kinetic geo synthetic (EKG) technology has been used to successfully stabilize a failing clay embankment in London resulting in a 26% cost reduction and a 47% reduction in carbon footprint over conventional methods.

o A trial was conducted on a 22m stretch of

a 9m high Victorian embankment. The

embankment had been constructed by end

tipping a mixture of weathered London

Clay and other material such as brick and

stone fragments onto underlying alluvium

and terrace gravels.

EKG TREATMENT

EKG treatment was designed to accommodate either of

the identified failure mechanisms. The treatment was

based around an array of EKG electrodes installed at 2m

centers in the form of tessellating hexagonal cells, with

the hexagon being defined by anode stations and a

central cathode

EKG anode/cathode installations using a P45 drill rig.

Results after treatment:

o Dewatering from the cathodes >25 times that from control drains.

o A reduction in plasticity and shrinkage characteristics.

o An increase in groundwater temperature from 10°C to 20°C.

o A modest DC power consumption of only 11.5kWhrs/m³ of soil treated.

o Improvements in shear strength parameters (c’ and Φ)

o A 263% improvement in the bond strength of the anodes acting as nails

o A cessation of slope movement.

o Following EKG treatment the anodes have been retained as permanent soil nails and the horizontal cathodes retained to act as permanent drainage

Analysis :

Analysis Reinforcement FoS (ULS)

Pre treatment

(TGP data)No 0.81

Pre EKG treatment No 0.96

Post EKG

treatmentNo 1.47

Post EKG

treatmentYes 1.71

Slope stability analyses were undertaken pre and post treatment. The

analytical results are shown in the table below.

Longevity of treatment

The use of EKG to stabilize slopes is a long term solution because:

o Soft weak embankment materials consolidate and improve in shear strength with EKG treatment. This consolidation is permanent.

o Additionally, EKG treatment works best on these soft materials, which are critical to the stability, and in this way the treatment can be considered ‘self selecting’

o Enhancement of soil/reinforcement bond is a long term effect.

o Passive drainage (de-activated cathodes) is retained in the slope.

Costs

o EKG treatment produced total project cost savings of 26% than lowest cost alternative of gabion baskets .

Carbon Footprint

o A carbon footprint comparison of the EKG and conventional treatment options showed 47% lower emissions by using EKG.

Dewatering of sewage sludge

(a) Conventional treatment, 19% dry solids content; (b) EKG enhanced treatment, 31% dry solids and 39% volume reduction.

Dewatering of mine tailings

Disposal of kimberlite slimes Dewatered tailings (78%) dry solids.

Conclusion

o Active geo synthetics in the form of

EKG materials open up a new range

of applications for geo synthetics.

o EKG applications relate to a number

of main drivers including legal

requirements, climate change, the

need to reduce carbon footprints,

reclamation of water and reduction

and reuse of wastes.

References:

o Mumtaz .m et.al,Performance evaluation of

coir as electro kinetic geo textile.

o Colin j.f.p.jones et.al,Electro kinetic geo

synthetics in hydraulic applications.

o Huntley ,D.T& Lamont-Black ,J, Economic

models for the use of electro kinetic geo

synthetics.

o Mumtaz M et.al ,Electro kinetic geo textile

stabilization of embankment slopes.