Environmental Engineering Reference
In-Depth Information
1.6
Use of Electrokinetics for Stabilization of
Week Grounds
Casagrande (1930) found that a permanent stabilization of soil could be
obtained by using aluminum electrodes. These aluminum electrodes were
found to be greatly corroded and aluminum compound deposits were noticed
around the electrodes. Encouraged by the model tests, Casagrande (1937)
undertook a full scale experiment and came to the conclusion that electro-
chemical treatment could be used for increasing the bearing capacity of piles.
Casagrande (1960) attributed the increase in the bearing capacity of
piles after electrochemical treatment to the following:
1. Water was transported from one electrode to another, caus-
ing a change in the water saturation.
2. The loosely attached low valence ions to the clay-plate surface
were displaced with higher valence ions by base exchange,
such as the replacement of Na ions by Al ions.
3. Metal derivatives were deposited around the anode and
CaCO 3 around the cathode, acting as cementing agents
between soil particles.
Probably, the best example of the use of electrokinetics to increase the
bearing capacity of piles was in a bridge foundation over the Big Pic River,
near Marathon, Ontario, Canada (Casagrande et al., 1950). The ultimate
bearing capacity of piles driven 110 ft into the ground was constant over a
one-year period at 30 tons. The piles were about 23 ft apart. A potential of
100-volt tension was used to give an average current of 15 amps per pile.
The bearing capacity of the piles increased from 30 to 100 tons after this
treatment was maintained for four weeks.
Russian scientists have made significant contributions to the investi-
gation of the electrochemical stabilization of soil and the induration of
weak rocks, through the continued addition of different electrolytes at
the anodes and by the use of electrodes of various materials. Tolstopiatov
(1940), Zhinkin (1952-1959), Rebinder (1957), Titkov et al. (1961) and
others seem to agree that upon electrochemical treatment, soil and weak
rocks underwent major physicochemical changes. All investigation indi-
cated that these physicochemical changes led to the formation of a new
soil structure (coagulation-crystallization structure). Zhinkin (1958) fur-
ther indicated that these changes were irreversible, and that more strength
was obtained progressively by the newly-formed clay structure even after
the discontinuation of electrochemical treatment.
 
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