Geotechnical and Geophysical Properties of Soils in the Dead Sea Sinkhole Problem

Abstract

Geotechnical and geophysical properties of Dead Sea (DS) sediments are of a great importance in the DS sinkhole problem. DS sinkholes are formed on the alluvial fans and mud flats. The first are composed of sandy-gravel sediments. Second ones are brine saturated lime carbonates. We reveal following features of the DS soil properties. Sandy-gravel sediments are presented by coarse sands, which are characterized by Vs = 300 – 650 m/s. Such increased shear wave values can be caused by increased the soil stiffness described in the literature. Brine saturated lime carbonates (DS mud) are characterized by low Vs values of 120 – 250 m/s. They do not exhibit cohesion. It is explained by mineralogical composition of the Dead Sea material, composed predominantly of calcite and not clay minerals, whereas other Israeli clays are comprised largely of montmorillonite (spectite) clay minerals. This feature allows considering of saturated lime carbonate as cohesionless soil like fine sands. Lime carbonates demonstrate also very low cation exchange capacity (CEC) that allows use of TEM resistivity method for determining of porosity of both sands and DS mud. Note also that significant difference of Vs in sands and lime carbonates allows mapping of different lithology along DS coastal areas.