An application of a fuzzy classification routine suggested for fine grained soils

Abstract

Soil classification is an important stage in preliminary studies for design applications in engineering geology. A few letters or numbers assigned to a soil provide rapidly an idea to engineers. The classification of fine grained soils in national and international soil classification systems is determined using plasticity chart. However, because of the factors affecting liquid and plastic limit tests, uncertainties can arise in classification of fine-grained soils when this approach is used. Furthermore, uncertainty level has increased in case points fall sometimes on the lines or near the lines. In this study, an application of a fuzzy classification routine which was suggested before to minimize these uncertainties was performed. In the suggested method, the spatial distances of the evaluation points on the chart from the lines were considered. The membership degrees that define the fuzzified soil and plasticity were determined by using sigmoid function. Finally, fuzzy soil classes were obtained by using fuzzy operators. The suggested fuzzy classification routine, was performed on classification of 100 fine-grained soil samples ad obtained fuzzy soil classes were compared with crisp soil classes.