COMPUTATION OF PLASTIC LIMIT USING MATHEMATICAL MODEL
This paper presents a mathematical model that uses a British cone to predict the soil moisture-penetration relationship. This relationship is nonlinear for non-bentonite bearing soil and can be modelled using a sigmoidal mathematical function. The developed mathematical model gives a unique opportunity for computing and predicting the fall cone penetration of the soil even at a very low moisture content, at which, due to practical limitations, it is impossible to determine the soil penetration. The mathematical model was found to fit the moisture-penetration data reasonably well. Based on the data presented in this paper, both the liquid limit and plastic limit can be determined from the extended liquid limit flow curve by determining the plastic limit at a 1.2 mm penetration value. The computed plastic limit at a 1.2 mm penetration value was found to be in close agreement with the measured plastic limit.