Preferred Design Procedure
Currently, there is no FHWA guidance that addresses the design procedure(s) for electroosmosis. However, various design procedures have been published in the literature as summarized below that lead to the details required for installation and operation of an electroosmosis system to achieve some specified amount of (depending on the application) consolidation, ground strengthening, drainage, settlement, etc., within some period of time.
These procedures do not provide the required soil engineering property values. These come from the overall project requirements that are usually determined by other, more traditional geotechnical and pavement analyses. These procedures have been applied in very limited fullscale projects but are valid for the following applications:
- Pavement foundation stabilization.
- Construction working platforms.
- Recycling/reuse (e.g., dredged fill).
- Increasing support of embankment or structures.
- Reduction of post-construction settlement.
- Earth retention.
- Slope stabilization.
- Thickness reduction of pavement overlays.
- Prolonging pavement service life.
Verification and improvements to these design procedures through field studies are highly warranted. Electro-osmosis can be combined with chemical-osmosis (also referred to as electro-kinetic stabilization) or with bio stabilization methods, which can be used for voidfilling applications, especially to fill voids under pavements. A design procedure for this application has not been developed; however, the field-trial-based design as described below could be implemented. Table 1 provides the typical inputs and outputs for the design and analysis procedures.
Table 1. Typical inputs and outputs for design and analysis procedures
Performance Criteria/Indicators
Moisture content and density
Shear strength / bearing capacity / California bearing ratio
Stiffness / modulus
Settlement
Water discharge
Pavement deflections (under static or dynamic loading)
Degree of consolidation
Ground water level
Lateral movement
Liquefaction potential
Subsurface Conditions
Delineation of Stratigraphy
Soil Classification
Water Content
Organic Content
Groundwater elevations
Coefficient of Consolidation
Permeability/Hydraulic Conductivity (may also need to measure electro-osmotic permeability)
Undrained Shear Strength, su
Electrical Resistivity
Liquefaction potential
Young's Modulus
Corrosion Potential of Soils
Atterberg Limits
Compression index/compression ratio
Effective Internal friction angle, ϕ'
Gradation
Recompression index/Recompression ratio
Unit weight
Loading Conditions
Structure/embankment load/traffic loading
Earthquake acceleration and duration
Material Characteristics
Stratigraphy (treatment depth)
Soil classification (Atterberg limits and particle size distribution)
Water content (saturation) and density (or void ratio)
Organic content
Groundwater water level
Coefficient of compressibility consolidation
Permeability (electro-osmotic and hydraulic)
Shear strength / bearing capacity
Electro chemical properties
Soil conductivity and electrical-soil resistance (change with time)
Failure plane location (slope stability)
Liquefaction potential
Type of electrodes
Discharge capacity at cathodes
Stiffness/modulus
Construction Techniques
Electrode installation
DC power source
Water discharge wells / trenches
Pumps
Time of treatment
Geometry
Electrode spacing
Electrode layout
Electrode length
Potential failure plane
References
Barker, J.E., Rogers, C.D.F., Boardman, D.I., Peterson, J. (2004). “Electrokinetic stabilization: an overview and case study.” Ground Improvement, Vol. 8, No. 2, 47–58.
Bjerrum, L., Moum, J., and Eide, O. (1967). “Application of electro-osmosis to a foundation problem in a Norwegian quick clay,” Géotechnique, Vol. 17, No. 3, 214–235.
Casagrande, L. (1983). “Stabilization of soils by means of electro-osmosis – State-of-the-art,” Boston Society of Civil Engineers Section, ASCE, Vol. 69, No. 2, 255–302.
Chappell, B.A., and Burton, P.L. (1975). “Electro-osmosis applied to unstable embankment,” Journal of the Geotechnical Engineering Division, ASCE, Vol. 101, GT 8, 733–740.
Dearstyne C. S. and Newman G. J. (1963). “Subgrade stabilization under an existing runway,” Journal of the Aero-Space Transport Division, ASCE, Vol. 89, No. AT1, 1–8.
Glendinning, S., Jones, C., Pugh, R. (2005). “Reinforced soil using cohesive fill and electrokinetic geosynthetics,” International Journal of Geomechanics, Vol. 5, No. 2, 138–146.
Jones, C., Glendinning, S., Huntley, D.T., and Lamont-Black, J. (2006). “Soil consolidation and strengthening using electrokinetic geosynthetics – concepts and analysis,” Geosynthetics: Proceedings of the 8th International Conference on Geosynthetics 2006, Ed., Kuwanao, J., and Koseki, J., Millpress, Rotterdam, 539–542.
Lo, K.Y., Ho, K.S., and Inculet, I.I. (1991). Field test of electroosmotic strengthening of soft sensitive clay,” Canadian Geotechnical Journal, Vol. 28, 74–83.
O’Bannon, D. E. Morris, G. R., and Mancini, F. P. (1976). ‘‘Electrochemical hardening of expansive clays.’’ Transp. Res. Rec. 593, Transportation Research Board, 46–50.
Pugh, R.C. (2002). The application of electrokinetic geosynthetic materials to uses in the construction industry, Ph.D. Thesis, University of Newcastle upon Tyne, U.K.