Centrifuge model tests on soil-nailed slopes subjected to seepage

Abstract

This paper presents the results of centrifuge model tests on the behaviour of a slope subjected to seepage with and without soil nails. For this purpose, a custom-designed seepage flow simulator was developed for evaluating the deformation behaviour of slopes with and without soil nails at the onset of seepage flow at 30g. A series of centrifuge model tests was carried out on 2V:1H slopes by varying nail layout and length of soil nails. Bored and grouted soil nails including nail heads were modelled using thin aluminium tubes covered with a thin layer of sand-coated adhesive. A soil nail inclination of 15° with the horizontal was adopted with two different layouts. All the models were thoroughly instrumented with displacement transducers for measuring settlements and using pore pressure transducers to capture the development of the phreatic surface within the slope during the centrifuge test. A digital image analysis technique was employed to arrive at displacement vectors of markers placed on the front elevation of the slope. The displacements were used to compare slopes with and without soil nails and to identify the occurrence of failure surfaces. The results indicate that stabilising the earth slope using soil nails has a significant effect in improving the stability and deformation behaviour of a slope subjected to seepage. For a soil nail layout, the stabilising effect was observed to diminish with a decrease in soil nail length and increasing vertical and horizontal spacing of the soil nails in the slope surface. Stability analysis of the slope models with and without soil nails was found to be in good agreement with physically observed centrifuge test results.

Centrifuge model studies on soil-nailed slopes subjected to seepage

“…It was reported that an increase in the nail inclination could not prevent the formation of crack on the crest and measured settlements were observed to increase with an increase in nail inclination. Deepa and Viswanadham (2009) conducted centrifuge model tests with and without soil-nails and presented that increase in vertical as well as horizontal spacing of nails and decrease in nail length reduced the stabilizing effect. Rotte and Viswanadham (2013) reported that slope facing helped to retain the soil mass effectively behind it and it prevented the local failure of the soil between the nails at the toe of slope.…”

“…In the present study, a model container with internal dimensions of 760 mm in length, 200 mm in breadth and 410mm in height was used for making slope models at normal gravity. The other details of the strong box and the procedure followed to reduce the friction effects and to approximate plane-strain conditions can be obtained from Deepa and Viswanadham (2009). In the present study, seepage simulator unit available at centrifuge laboratory was used to induce seepage within the slope models with and without soil nails.…”

Centrifuge and Numerical Model Studies on the Behaviour of Soil-Nailed Slopes with and without Slope Facing

“…A strong box of 0.76 m long, 0.20 m wide and 0.41 m high internally was used for the experimental program. The other details of the strong box and the procedure followed to reduce the friction effects and to approximate plane-strain conditions were discussed by Deepa and Viswanadham (2009). A seepage simulator unit was used to allow seepage of water through soil-nailed slopes during the tests.…”

Centrifuge model studies on anchored geosynthetic slopes for coastal shore protection

“…In order to minimize this problem, both internal sides of walls were covered with a thin layer of white petroleum grease and thin polythene sheet strips of 100 mm width. With this arrangement, the friction effects can be reduced, and plain strain conditions can be approximated (Deepa and Viswanadham, 2009). Fig.…”