AN ARRANGEMENT FOR MEASURING SWELL PRESSURES EXERTED BY EXPANSIVE SOILS

The note describes a new arrangement of using a hydraulic oedometer together with a hydraulic pressure generating unit for studying the swell behaviour of expansive soils. The hydraulic oedometer (model wf 2450), is marketed by Wykeham Farrance Engineering Limited, England, and is of the type developed at Imperial College, London. It is modified so that electrical leads from the brass probes are taken out of the apparatus. The pressure generating unit consists of A motorised gear box driving a threaded shaft in a screw-jack. A piston moving in a watertight cylinder is attached to the screw-jack. The unit is capable of generating hydraulic pressures up to 1000 pounds per square inch. As the sample swells it lifts a brass plate and makes contact with the brass probes completing the electrical circuit. The gear box then drives the screw-jack generating a pressure which is transferred back to the oedometer to compress the soil to its original thickness. The electrical contact is broken when this is achieved. The process is continued till the maximum swell pressure is attained. Readings of swell pressure and volume of water imbibed are taken at various time intervals. /TRRL/