Abstract
In this experimental work, we investigated the effects of various fall cone parameters such as cone apex angle, diameter, overload, cone surface roughness on Atterberg Limits of both homogeneous and non-homogenous (layered) type soil samples. The liquid limit of cohesive clayey silt as well as silty-clay soil samples were determined based on fall cone tests with four different cones with 30 o and 60 o apex angles, two different diameters and also different surface roughness. The results showed that the apex angle of cone may play a more important role in determining the Liquid limit of soil. Furthermore, it is found that the dropped cone behavior in soil sample changes from a dynamic to quasi-static by increasing the cone apex angle from 30 o to 60 o . It is also shown that the penetration vs. moisture content response curves in non-homogenous type soil samples have changed rather considerably near the boundary of layers compared to the homogeneous soil counterparts. The results of this study have also shown that this variation would depend on the layering structure of soil. The current study has also shown that for non-homogeneous soils 20mm penetration may not be accurate for determining the liquid limit of soil compared to homogeneous samples. The findings also indicated that fall cone test results may also be applied for determining the plastic limit of clayey and silty soil samples. The obtained results based on different cones might also be used to determine the undrained shear strength (S u) of clayey or silty soil samples at the lower bound limits of penetration vs. moisture content curves.