The behavior of a steep sandy slope remediated by a hybrid lightweight fill under seepage was investigated by using physical slope models. The fill was comprised of expanded polystyrene (EPS) blocks (geofoam blocks) with internal drainage channels and EPS bead – sand mixture. The dimensions of the geofoam blocks (density of the blocks were 20 kg/m3) used in hybrid lightweight fill were 2.5-cm high, 5-cm wide, and 15-cm long. Two 0.5-cm wide and 15-cm long drainage channels were grooved along both top and bottom of these blocks. EPS bead content used in EPS bead – sand mixture of the hybrid lightweight fill system was 0.5% by weight. The hybrid lightweight fill was assembled to form an “embankment type configuration” at the toe of the sandy slopes. In this configuration, the geofoam blocks were placed along the slope face whereas the EPS bead – sand mixture was compacted to form the back-slope. In order to generate the hydrologic conditions within the slope, a laboratory lysimeter with dimensions of 60-cm high, 20-cm wide, and 200-cm long was constructed using 1-cm thick acrylic glass. Constant pressure heads of 25 cm-, 38 cm-, and 50 cm-H2O were applied at the water reservoir compartment of the lysimeter during the tests. Two different embankment heights (15-cm and 22.5-cm) were used to investigate the effect of seepage on the dimension of the lightweight assemblage. The performance of the hybrid lightweight slope system was compared to that of non-remediated slopes.
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