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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #326532
Title: Behavior of fiber reinforced sandy slopes under seepage

Author
item AKAY, ONUR - Okan Universitesi
item OZER, TOLGA - Okan Universitesi
item FOX, GAREY - Oklahoma State University
item Wilson, Glenn

Submitted to: Environmental and Water Resources Institute World Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2016
Publication Date: 5/13/2016
Citation: Akay, O., Ozer, T., Fox, G.A., Wilson, G.V. 2016. Behavior of fiber reinforced sandy slopes under seepage. Environmental and Water Resources Institute World Congress Proceedings. pp. 397-406.

Interpretive Summary: Seepage is a major cause of natural hill slopes, river banks and engineered embankments failing. In order to increase the factor of safety, a new technology involves the inclusion of man-made fibers in the soil. The addition of such fibers has a favorable effect on the strength of sandy soils. In this study, laboratory experiments were conducted in plastic boxes on fiber reinforced soil with two different values of water levels (25 cm and 50 cm) in the water reservoir. Fiber reinforced sand was compacted in the soil compartment of the box to obtain a slope with dimensions of 55 cm height, 20 cm width, and 100 cm base length. The fiber content (percentage of fiber per weight of dry sand) was selected as 1% after reviewing the results of compression tests on fiber reinforced sand samples 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 overall factor of safety. The compression tests measured the increase in peak stress with increase in fiber content. The fiber reinforced sand in the experiments was stable against seepage conditions which would otherwise cause a shallow failure of the non-remediated slope under 25 cm water pressure head. However, the soil with fiber showed a shallow failure under 50 cm water pressure head, whereas a deep-seated failure occurred for the non-reinforced soil as soon as the water level was raised above the crest of the slope.

Technical Abstract: 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 cm 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 non-remediated slope under 25 cm water pressure head. However, instability manifested itself as a shallow-seated failure under 50 cm water pressure head, whereas a deep-seated failure occurred as soon as the constant water pressure head was raised above the crest of the slope.