Static and Dynamic Bahavior of Dry Saline Soil

Abstract

In this paper, two samples of dry natural saline soil were studied and physical and chemical tests were conducted. The first sample was from Diyala Governorate, Al-Khalis District, and was taken at a depth of 1 meter. This sample had a sodium chloride salt concentration of 54%. The second sample was prepared in the soil laboratory at the College of Engineering, University of Diyala, by mixing the first sample in known weight ratios with clean, salt-free sand to obtain a second soil sample with a sodium chloride salt concentration of 32%. After that, the container in which the laboratory tests were carried out was prepared and made locally with dimensions of 50 cm × 50 cm × 55 cm and was painted yellow. The behavior of the two samples was studied under static and dynamic loading. Through the latter, we knew the dynamic response parameters, represented by speed, acceleration, displacement amplitude, and settlement, all with respect to time. It was found that the behavior of the soil with a sodium chloride salt concentration of 54% was much weaker compared to the behavior of the soil with a sodium chloride salt concentration of 32%. The weakness is represented by an approximate percentage of about 50%. In the static state, the bearing capacity decreased from (48 to 32) kilopascals for the two percentages of 32% and 54%, respectively. However, it was also found that increasing the salt content in the soil leads to increased vibration amplitude, decreased damping, and faster sedimentation, especially at frequencies of 15 Hz and 20 Hz. These effects are attributed to the weak internal structure of the salt bonds between soil particles, which weaken rapidly under cyclic loading. At the end of the study, it was found that reducing the salt content of the soil in the laboratory by mixing it with clean, dry sand in known weight ratios significantly improved the soil properties and dynamic behavior. The results of this study have contributed to a better understanding of the behavior of dry sabkha soils for the design of better and safer foundations in areas where saline soils predominate.