Browsing by Author "Akay, O."

Now showing 1 - 2 of 2

Citation Count: 14
Assessment of EPS block geofoam with internal drainage for sandy slopes subjected to seepage flow
(Ice Publishing, 2014) Akay, O.; Ozer, A. T.; Fox, G. A.
Lightweight expanded polystyrene (EPS) block geofoam (geofoam block) is commonly used as a replacement of the heavy in situ soil during slope remediation in order to reduce driving forces. The design procedure requires the use of permanent drainage systems to alleviate hydrostatic pressures in geofoam block slope systems. In this study, small-scale laboratory lysimeter experiments investigated the behavior of a stabilized sandy slope with a geofoam block slope system experiencing seepage. An internal drainage system was incorporated by grooving dual drainage channels (weep holes) on the top and bottom side of the geofoam blocks. A lysimeter with dimensions of 60 cm height, 20 cm width, and 200 cm length was constructed in the laboratory. Slopes were constructed by compacting sand. The geofoam blocks (2.5 cm height, 5 cm width, and 15 cm length) were placed on the sandy slope face with an angle of 458 in 'one row' and 'two rows' configurations. The experiments were conducted under constant water pressure heads (25-, 38-, and 50-cm pressure head boundary conditions) in the water reservoir located at the opposite end of the lysimeter from the geofoam blocks. In general, the lightweight geofoam blocks could not resist earth and hydrostatic pressures under seepage. The back-slope was not selfstable under seepage conditions, and deep-seated global stability failures were observed, except for the remediated slope at the 25-and 38-cm pressure head boundary conditions. The internal drainage system was ineffective at dissipating piezometric pressures at the higher seepage gradients investigated at this lysimeter scale. Numerical slope stability modeling confirmed these observations, predicting a factor of safety below the critical value for global stability in cases where failure was observed. More elaborate geofoam block configurations and/ or drainage systems should be used to increase resistance against global stability failure caused by higher seepage gradients.
Citation Count: 18
Slope stabilisation using EPS block geofoam with internal drainage system
(Ice Publishing, 2016) Akay, O.
Lightweight expanded polystyrene (EPS) geofoam (geofoam block) is used in slope remediation works as a soil substitute fill to reduce driving forces that can lead to global instability. On the other hand, the presence of seepage flow requires special attention because geofoam block slope systems are vulnerable to seepage-induced lateral forces. In this study, the effect of an internal drainage system on the alleviation of piezometric pressures within the back-slope of a geofoam block slope system was investigated. For this purpose, laboratory experiments were conducted using a small-scale lysimeter with dimensions of 60 cm height, 20 cm width, and 200 cm length. The slope was compacted with sand to obtain an overall dry unit weight of 14 kN/m(3). The constant piezometric head boundary conditions of 25, 38 and 50 cm generated the necessary hydraulic energy gradient for the seepage flow directed from the water reservoir of the lysimeter to the 45 degrees angle slope face. The slopes were remediated by using geofoam blocks assembled in an embankment-type configuration at the toe of the slope. The internal drainage system consisted of grooved geofoam blocks that formed the 10, 15 and 22.5 cm high embankments. Deep-seated failures of the non-remediated slope were prevented except for the experiments with 10 and 15 cm high embankments under 50 cm pressure head boundary conditions. In general, the internal drainage system alleviated the piezometric pressure conditions within the back-slope by lowering the phreatic surface using the active drainage channels observed during laboratory experiments. These drainage channels provided a convenient passageway for seepage flow. The coupled numerical variably saturated flow modelling and slope stability modelling predicted the factor of safety for global stability which confirmed the observed physical conditions in the laboratory. The use of the internal drainage system increased the factor of safety of the geofoam block slope system under seepage conditions.