Shear modeling of polypropylene-fiber-reinforced soil composite using electrical conductivity contour technique

Randomly distributed fiber-reinforced soils have recently attracted increasing attention in geotechnical engineering for the second time. On the basis of predictive models that have been presented till now, shear strength of fiber-reinforced soil increases with increase in fiber aspect ratio, fiber content, fiber modulus, and soil fiber surface friction. The main aim of this paper is therefore shear modeling of polypropylene-fiber-reinforced soil composite by considering the fiber orientation parameter. Force equilibrium method proposed by Waldron was extended to predict shear behavior of randomly distributed fiber–soil composite. The fiber orientation factor was derived by using electrical conductivity contours as a novel technique. In electrical conductivity contour method, electrical conductivity is measured between different points through the soil composite. After that a visual matrix is drawn that shows the uniformity of fiber distribution within the soil matrix. The experimental shear tests revealed that the shear strength of 19-mm polypropylene-reinforced soil composite is less than that of 6 - and 12-mm reinforced samples. On the other hand, electrical conductivity contour method showed that polypropylene fibers of 19-mm length present the worst fiber distribution compared to 6-mm and 12-mm fibers. Therefore, the theoretical model was modified with an orientation factor.