Performance Evaluation of Reinforced Expansive Soil Subgrade with Polypropylene Fiber and Geogrid

Abstract

The rapid development of infrastructure often encounters the loose soil subgrade and is becoming difficult to carry to construction activities. Various mechanical and chemical methods have been developed to reduce the impact of the expansive soil. Mechanical stabilization of expansive soils by reinforcing with polypropylene fibers and geogrid is one of the sustainable solutions. Geogrids and polypropylene fibers have been extensively used to reinforce the expansive soil subgrade and foundations as individuals. The polypropylene fiber reinforcement enhanced the tensile strength capacity of the reinforced expansive soil wherein the geogrid reinforcement is the quick fix mechanical stabilization technique, which reduces pavement failures. In this research, the combined effect of the polypropylene fiber and geogrid reinforcement has been evaluated to stabilize the pavement subgrades. Various mechanical strength tests such as unconfined compressive strength (UCS) and large direct shear box tests were conducted to evaluate the mechanical interaction between expansive soil subgrade, polypropylene fiber, triaxial geogrid, and biaxial geogrid at the interface. Polypropylene fiber of 12-mm length was used in the proportion of 0.25, 0.5, and 1.0% and single share geogrid layer at mid-depth. The result shows that the shear strength of reinforced subgrades with a layer of biaxial/triaxial geogrid and polypropylene fiber increases significantly. It is also observed that the unconfined compressive strength of the expansive soil increased with the inclusion of polypropylene fiber and geogrid. The combined reinforcement method shows an effective treatment methodology to improve the engineering property of expansive soil subgrades.