Strength and Compaction Behavior of Randomly Distributed Polypropylene Fiber-Reinforced Expansive Clay

Experimental investigations were conducted to study the effects of randomly distributed polypropylene (PP) fiber inclusions on the mechanical behavior of expansive soil. Reinforced soil specimens were prepared at four different fiber contents (0.05, 0.1, 0.15 and 0.2%), and the aspect ratio of fibers (L/D) was kept as 250. A series of compaction tests, unconfined compressive strength (UCS) and split tensile strength (STS) tests were performed on the unreinforced and fiber-reinforced soil specimens. The results proved that the UCS and STS values increased to a greater extent with the inclusion of fibers to the expansive soil. The inclusion of monofilament-type PP fibers within expansive soil contributes to increase the peak axial stress, improve the residual strength and increase the modulus of elasticity, toughness and ductility of the soil. It was noticed that the effect of polypropylene fiber inclusion on the compaction parameters was not much significant (less than 5% variation) due to lightweight and less water absorption capacity of PP fibers. The highest UCS values were obtained with 0.15% fiber content with 12 mm length of fibers for that UCS values increased up to 51% of that of the unreinforced soil. Similar behavior was also observed for STS of soil–fiber mixtures with a gain of 59% in tensile strength. From the UCS and STS test results, some other parameters like secant modulus, shear modulus, resilient modulus and deformability index were also reported for both unreinforced and reinforced specimens. It was seen that secant modulus of expansive soil increased up to 89% and resilient modulus was increased up to 17% on addition of 0.15% fibers. Similarly, other parameters were also improved with the inclusion of PP fibers within the expansive soil.