MEASUREMENT OF COEFFICIENT OF EARTH PRESSURE AT REST IN CLAYS

Abstract

An experimental study for determining the coefficient of earth pressure at rest has been carried out for a local plastic clay, both during triaxial and consolidation tests. A lateral strain indicator was used for determination of Ko during triaxial tests. For this purpose, an automatic elect-ronic switching unit was designed and fabricated for applying the cell pressure automatically at slow and uniform rate to maintain zero lateral strain condition. The values of Ko conform to those reported by Bishop and Henkel (1957). Lateral pressure during consolidation test was also measured with the help of strain gauges fixed and covered with wax on the outside periphery of the consolidometer ring cast out of duralumin. An apparatus for calibrating the consolidation .ring was , therefore, designed and fabricated. Although the lateral pressures measured during the test do not give appropriate value of Ko, but they were found within acceptable limits and have shown a definite trend of variation during primary as well as secondary consolidation. Lateral pressure was found to increase during secondary consoli-dation. A theoretical relationship has also been developed bet- ween degree of consolidation ~,.~ and tine factor for linearly vary- ing load to assess duration of K. triaxial test