Assessment of Some Geotechnical Properties for Soils of Euphrates River Banks (Kufa- Mishkhab), Middle of Iraq

Abstract

Twelve stations in the cities of Kufa and Mishkhab were selected for studying the geotechnical, including physical, engineering, chemical and mineralogical, properties of soils in the river banks along the Euphrates River. Grain size distribution of the bank soils showed higher silt than clay and sand percentages. Soil samples from the 12 stations were classified according to the USCS standards. Silt with low plasticity constituted 91% of the silt fraction, whereas that with high plasticity composed 9%. The saturated density values ranged between 1.75-2.073 g/cm³ with an average of 1.953 g/cm³, while the dry density values ranged between 1.307-1.740 g/cm³ with an average of 1.553 g/cm³. The values of the dry and saturated density are within the permissible limits. Direct shear test showed cohesion values (C) that ranged between 15-55 kN/m² with an average value of 34.8 kN/m². The values of the internal friction angle (Ø°) of the clay type of soil with low plasticity ranged between 8.5°-17° with an average of 9.91°. The Ø° values of the other soil types ranged between 9°-17° with an average of 25°. Therefore, clay with high plasticity had higher Ø° values than the permissible limits. The results of unconfined compression test showed a range of 22.802-58.587 kN/m² with an average of 38.173 kN/m², with water percentage of 30%. The mineralogical tests of the bank soil performed using XRD analysis showed that the analyzed soil samples are composed mainly of quartz, calcite, chlorite, palygorskite, and montmorillonites. The pH value ranged between 6.4-7.55 with an average of 7.10, indicating low basicity. Gypsum concentrations ranged between 0.049-12.75 % with an average of 3.99 %, while that for carbonate ranged between 5-45 % with an average of 26.16%. Sulphates concentration ranged between 0.23-5.93 % with an average of 1.85%. Several treatment measures are proposed to stabilize the soil of the studied area.