Experimental Investigation of the Mechanical Properties of Polypropylene Fiber-Reinforced Clay Soil and Development of Predictive Models: Effects of Fiber Length and Fiber Content

Abstract This study investigated the mechanical properties of a low plasticity clay soil reinforced with polypropylene (PP) fiber in various contents (0.05%, 0.10%, 0.15%, 0.20%) and lengths (6, 12, 19 mm). The reinforced specimens were subjected to unconsolidated-undrained (UU) triaxial compression tests under three different confining pressures (50, 100, and 200 kPa). The optimum fiber contents in specimens reinforced with 6, 12, and 19 mm PP fiber were determined as 0.15%, 0.15%, and 0.20%, respectively. As a result, the highest values regarding deviator stress at failure (σdev), energy absorption capacity (EAC), and shear strength parameters occurred in specimens containing 0.20% PP (19 mm). As a result of the reinforcement process, the most remarkable improvements in the σdev, cohesion, internal friction angle, and EAC values of the natural soil are 59.95%, 21.80%, 63%, and 34.70%, respectively. Linear and non-linear relationships between σdev and fiber length, fiber content, and confining pressure were investigated by multiple linear regression (MLR) and artificial neural network (ANN) methods. Equations were generated to predict σdev of a low plasticity clay soil reinforced with PP fiber and were made available to geotechnical researchers.