Statistical Analysis of Influenced Factors Affecting the Plastic Limit of Soils

Abstract

The determination of plastic limit of soils according to ASTM Standards specifies the value of plastic limit as the moisture content of rolled soil thread at 3.2 mm diameter that begins to crumble. The reliability of test results must depend on the skill of operator and various mechanical factors. In practice, test results of plastic limit have a high variation. In this research, influenced factors on the variation of results were studied. Statistical analysis of results by multiple regression, correlation, and analysis of variance indicated that there were two primary factors affecting the plastic limit of soils. The main factor was the initial size of the soil sample, explained 40% variation of the plastic limit value. The second factor was the type of soil classified by plasticity explained 21.8 % variation of the value. The other mechanical factors such as friction, speed, and pressure explained 3.0-3.2 % variation of the plastic limit value of soils.