Behavior of sandy slopes remediated by EPS-block geofoam under seepage flow

Abstract

Expanded polystyrene (EPS) geofoam (geofoam block) is commonly used as a lightweight fill for many civil engineering applications. However, when used for slope remediation, the behavior of geofoam block for slope systems undergoing seepage flow is not well known. In this study, a total of 36 laboratory lysimeter experiments (dimensions of 60 cm height, 20 cm width, and 200 cm length) were conducted to investigate the behavior of sandy slopes containing geofoam blocks as a lightweight fill material. These experiments were conducted with three different values of constant water pressure in the water reservoir located at one end of the lysimeter. In addition, three different configurations of geofoam block were tested with geofoam blocks placed on the face of the packed sandy slope. The dimensions of the geofoam blocks were 2.5 cm high, 5 cm wide, and 15 cm long to achieve a 1:20 scale corresponding to actual block size that is commonly manufactured. Laboratory physical test results were quantified by coupled seepage flow and slope stability models showing the adverse effect of seepage on the factor of safety (FS). Geofoam block configurations were found to be stable against seepage conditions which would cause a shallow-seated failure of the slope in the absence of the geofoam blocks. This is due to the fact that the geofoam blocks could completely fill the mass of the existing slope material subjected to failure. However, the geofoam block configurations were unstable against seepage conditions that resulted in deep-seated failures of marginally stable, sand slopes.