Behavior of Fiber-Reinforced Sandy Slopes under Seepage

Seepage flow is a major contributor to instability of natural hill slopes, river banks and engineered embankments. In order to increase the factor of safety, an emerging technology involves the inclusion of synthetic fibers in the soil. The addition of tension resisting fibers has a favorable effect on strength properties of sandy soils. In this study, laboratory lysimeter experiments were conducted on fiber reinforced slopes with two different values of constant pressure head boundary condition (25 and 50 cm) in the water reservoir. Fiber reinforced sand was compacted in the soil compartment of the lysimeter to obtain a slope with dimensions of 55 cm height, 20 cm width, and 100 cm base length. The gravimetric fiber content (percentage of dry weight of sand) was selected as 1% after reviewing the results of comprehensive triaxial compression tests on fiber reinforced sand specimens with varying fibrillated polypropylene fiber (12 mm long) contents from 0.1 to 1%. This study included slope stability modeling in order to quantify the global factor of safety. The triaxial compression tests indicated the increase in peak deviatoric stress with increase in fiber content. The fiber reinforced sand slope was stable against seepage conditions which would otherwise cause a shallow-seated failure of the nonremediated slope under 25 cm water pressure head. In addition, fiber reinforced sand slope maintained its global stability under 50 cm water pressure head which caused a deep-seated failure of the unreinforced slope. However, sloughing at the toe occurred under 50 and 55 cm water pressure head.