The Shear Strength Parameters as a Function of the Volumetric Water Content of Baghdad City Soils at Tigris River Bank

Abstract

The capital of Iraq, Baghdad city, is considered one of the regions with a diverse soil composition besides the various characteristics of these soils. The subbase layers can be divided into three zones that are fully saturated, partially saturated, and dry state. This research accomplishes the investigation and assessment of the geotechnical attributes of soil layers of the city, where these characteristics are associated with the ground water elevation. The water level disparity of the Tigris River was correlated with variation of the ground water level and with geotechnical results of more than 260 boreholes. The analysis of the output data revealed that undrained shear strength parameters of soil layers near the Tigris river bank is controlled by the flocculation of the water in the river. New relationships were developed associating the volumetric water content (VWC) with shear strength parameters of these soils (cu and ϕ). These empirical equations show that predicting strength compounds of partially saturated soils as a linear relation for the angle of internal friction and nonlinear for soil cohesive function with (VWC). Where is an increase of the amount of saturation in the (VWC) results a decrease in strength properties for the soil (cu and ϕ).