Introduction to Electrokinetics - Electrokinetics for Petroleum and Environmental Engineers - page 12

in drying waterlogged soils for heavy construction. The development of
these practical applications has been largely due to the work of Casagrande
(1937-1960) who has carried out continuous research on their feasibility in
relation to various soil characteristics.
Literature on civil engineering, soil mechanics, and highway research
has reported investigations made by Winterkorn (1947-1958), Casagrande
(1937-1960), and others on the nature and scope of the electrical treatment
of soils.
Some examples of electrokinetics treatment in civil engineering are
described here for the purpose of illustration.
Railway cut, Salzgitter, Germany (Casagrande, 1947): Difficulties that
arose during the construction of a double-track railway cutting, in a
loose-loam deposit due to the flow of soft soil, were overcome by a large-
scale drying operation using electrokinetics. In sections of 100 m, well
electrodes 7.5 m deep and 10 m apart were used. Before the applica-
tion of electrical potential, the average rate of flow of water was 0.4 m 3 /
day/20 wells. An electrical potential, with an average tension of 180 volts
and average current of 19 amps/well, was applied. During an eight-week
period, the flow continued at an almost constant rate of 60 m 3 /day/20
wells, i.e., at 150 times the flow rate before the application of electrical
potential.
U-boat pen, Trondheim, Norway: Several attempts to make an excavation
about 14-meters deep in a very thick stratum of clayey silt interspersed by
seams of sand in the proximity of the sea were doomed to failure because
of the very active uplift phenomenon. The application of electrokinetics to
cause water to flow away from the excavation site was tried next. The salt
deposits, which increased the electrical conductivity of the soil, required
high consumption of current.
Before the application of electrical potential, the flow rate varied from
1 o 50 liters per hour per well. A current of 26 amps at 40 volts tension was
used. The application of current increased the flow rate up to 11-479 liters
per hour per well. The average power consumption was estimated to be 0.4
KW-hr per cubic meter of soil excavated.
Lime sludge deposits: Some tests were made by Casagrande on dewatering
lime-sludge deposits (Wulprath, Germany) having a uniform water content
of 120 % of dry weight. The application of electrical potential with 70-volt
tension and a current of 50 amps for 14 days obtained a 25 % decrease in
moisture content. The reduction lines of water content indicated that the
electrokinetics dewatering process took place uniformly along the lines of
equal potential strength.