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.本研究提出一种以英国锥（British cone）为测试工具的数学模型，用于预测土壤含水率-贯入度的关联关系。针对不含膨润土的土壤，该关联关系呈非线性特征，可通过S型数学函数进行建模。所提出的数学模型即便在极低含水率条件下，也为土壤落锥贯入度的计算与预测提供了可行路径——这类极低含水率场景受限于实际操作条件，无法直接测定土壤贯入度。经检验，该数学模型可较好地拟合含水率-贯入度实测数据集。基于本文呈现的试验数据，可通过确定1.2mm贯入度下的塑限值，从扩展液限流动曲线中同时推求液限与塑限。通过该模型计算得到的1.2mm贯入度下塑限值，与实测塑限结果吻合度较高。