Evaluation of Geological Engineering features of north Kalaleh Loess deposits at Golestan province with special attitude on the collapsibility and erodibility

Loess is a particular type of silty soils with porous structure and weak cohesion which has been deposited over different periods of Quaternary. From the geological engineering view points, these soils are problematic ones whose main geological engineering feature of these soils is their erodibility and collapsibility. Loess soils are the main deposits cover north of Golestan province. These soils have spread across 4200 square kilometers. In this study, in order to examine and identify the loessic soils, undisturbed samples were collected and transferred to the lab and then Atterberg limit, specific gravity, grading, percentage of lime, specific density, rate of consolidation, and shear strength parameters were determined. Soil collapsibility was also determined using the results of the double oedometer tests. According to the unified standard, these soils are categorized in CL and ML groups. Furthermore, based on Clevenger classification, they are placed in the category of clayey loess and silty loess. The amount of calcium carbonate in these soils ranges from 12 to 22.3 percent and demonstrates low shear strength parameters in saturated condition. The double oedometer tests results demonstrate that the soils are prone to collapsibility. The results of soil dispersion tests reveal that the depression, which is due to the presence of sodium carbonate, does not have any influence on erosion of mentioned soils; therefore the high erodibility of these soils is basically a mechanical phenomenon which can be attributed to special texture and grading of loesses.