Effect of Mica on K_O Compressibility of Two Soils

The effect of mica content on the compressibility of a sand and a silt under conditions of zero lateral yield consolidation was investigated. The sand tested was the medium, uniform, subangular Chattahoochee River sand, and the silt was a residual soil from the Atlanta, Georgia area. A special lateral deformation sensor was designed to be placed on a triaxial test sample and limit the lateral deformation to less than 0.001% Mixtures of from 0% to 50% mica in sand and 0% to 50% mica in silt were tested. The results of the sand series showed that for a given initial void ratio the compressibility was significantly increased by the addition of a small amount of mica, but K_O was not affected. For the silt series, partially saturated samples were formed under light static compaction. The results of the series showed no significant effect of mica content on the compressibility; however, there was a tendency for an increase in the coefficient of earth pressure at rest with increasing mica content.