Some mechanical properties of sandy gypseferous soils in Rumaila – Khor Al-Zubair area, southern Iraq.

Abstract

Six gypseferous soil samples were collected from Rumaila to Khor Al-Zubair areas, Didibba Desert West of Basrah city, Southern Iraq. These soil are gypseous in nature with an average gypsum content of 15.5 % w/w. The mineralogical analyses revealed that they are consisting of quartz, gypsum, carbonate, and feldspar. The grain size analysis showed that the sand fraction form more than 80% of soil samples understudy. Several geotechnical properties were determined. The testing program comprises the determination of the effect of the different gypsum contents on the shear strength parameters; cohesion and internal friction angle of the gypseferous soils under consideration. Furthermore, the testing program exhibits the cohesion increases as gypsum contents increases up to 20 % then decreases at 30 %. The results indicate that the improvement and deterioration of cohesion and shearing strength of soils are a result of the gypsum dual role, firstly bonding the soil particles, causing the and soil enhancement (up to 20 % added gypsum), and secondly causing the flocculation of soil particles leading to the deterioration (More than 20 % added gypsum) of cohesion and shear strength of the gypseferous soils.