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.