EXCAVATIONS: Electro-osmosis method.

This method is used for fine grained cohesive soils (such as clay), which can be drained or stabilised using electric current. The method was developed by L. Casagrande (1952). If direct current is passed between two electrodes driven into natural soil mass, the soil water will travel from the positive electrode (anode) to the negative electrode (cathode). The cathode is made in the form of well point or metal tube for pumping out the seeping form of well point or a metal tube for pumping out the seeping water. A steel rod, a pipe or steel piling of excavation can serve as the cathode. The arrangement of electrodes is done in such a way that the natural direction of flow of water is reversed away from the excavation, thereby increasing the strength of the soil and stability of the slope (Fig 2.41).

The potentials generally used in the process are from 40 to 180 volts, with electrode spacing of 4 to 5 metres.

FIG. 2.41 ELECTRO-OSMOTIC DRAINAGE.