Geotechnical Assessment of Soil Investigation at Campus Site of College of Science, University of Diyala, Iraq

Abstract

This study aims to evaluate some physical and mechanical properties of soil samples collected from the campus site of the College of Science, University of Diyala, Iraq. All laboratory tests were performed according to ASTM standards. The test results showed that the range of water content w was (13.89%-16.34%) and the specific gravity range was (2.58-2.77). Atterberg limits tests showed that the range of Liquid Limit LL, Plastic Limit PL, Plasticity Index PI were (26.20-35.20%), (18.63-23.24%), and (7.57-12.42), respectively. Liquidity Index LI values were ranged from 0.002 to 0.560, while Consistency Index CI values were ranged from 0.271 to 0.998 indicating a plastic state. The average optimum water content (OWC) and maximum dry density (MDD) obtained from the Standard Proctor Compaction test were 10.36% and 1.79g/cm3, respectively. Shear test results revealed that the cohesion strength range was (5-10) KN/m2 and the angle of internal friction range was (25-30o). The compression index derived from the consolidation test was ranged from 0.03 to 0.25, and the calculated values of void ratio (0.94-1.04) and porosity (0.48-0.51) are within the range of clay soils. According to the test results, the soil in the study area is classified as fine-grained soil type CL (i.e. inorganic clay soil of low to medium plasticity) based on USCS classification. The obtained OWC and MDD values from the compaction test can be used as criteria to control future filed compaction practice at the site. The calculated angle of internal friction values is within the range of CL soil. However, the cohesion strength is relatively low due to the high water content, as cohesion of clay soil is affected by water content and fine-grained content. The compression index values reflect the high compressibility of clay soil due to the high fine gained content, which is directly related to the settlement. Therefore, it is suggested to improve soil strength by increasing soil relative compaction not less than 95% to lower its compressibility and subsequent settlement, and increase its load bearing capacity. Finally, geotechnical parameters presented in the current study are discussed and compared well with previous studies. These parameters are helpful for future engineering works scheduled at the campus site of the College of Science, University of Diyala, Iraq.