A geotechnical study of evaporitic, lacustrine sediments in the saline environment of the Dead Sea area

Abstract

This paper is the third by the authors relating to the geotechnical properties of the evaporitic, lacustrine sediments of the saline environment in the Dead Sea area. The earlier papers identified difficulties involved in establishing the water content of sediments in a saline environment. A different approach was adopted whereby fluid content, rather than water content was used to define geotechnical properties. The present paper expands on the geological background presented in the previous papers, and discusses additional geotechnical aspects of the materials' behavior. The three major sediment types encountered in the region are fluvial granular soil, cohesive lime carbonate deposits and granular to massive halite sediments. The granular soils, composed predominantly of sand and pebbles of dolomite with minor chert and limestone, have gradations which vary widely both with depth and laterally. Shear wave velocities are higher than those estimated from common existing correlations with standard penetration test, SPT, blow counts. While compression indices, Cc, and cyclic shear response of the saturated lime carbonates are consistent with behavior of clay soils, their effective friction angle of about 34° on average, is significantly higher than that of clays. The geotechnical properties of the rock salts encountered in the region are shown to be intimately related to the extent of diagenesis and burial, with very significant difference between the younger, more porous deposits of Holocene age, and the older, Mt Sdom diapiric salt wall of Upper Miocene age. The latter are seen to have properties consistent with those of older rock salt deposits at greater depths, reported in the literature.