Centrifuge Model Studies on the Use of Hybrid-Geosynthetic Inclusions in Slopes Subjected to Infiltration: Fid-Bau Portal

Centrifuge Model Studies on the Use of Hybrid-Geosynthetic Inclusions in Slopes Subjected to Infiltration

Bhattacherjee, Dipankana / Viswanadham, B. V. S.

Rainfall-triggered slope failures have increased globally by over 70% in the last decade, as a direct implication of climate change. This can be counteracted by having good quality granular material to allow quick dissipation of pore water pressures. In the absence of permeable soils, the response of slopes with marginal soil during infiltration events can be improved by the simultaneous provision of preferential drainage channels and reinforcement function. The study discusses the effectiveness of inclusion of an assembled geosynthetic material possessing drainage action of a non-woven geotextile and reinforcement characteristic of woven geogrid, referred as a hybrid-geosynthetic. Centrifuge modelling technique was adopted, appropriate scaling laws were established, and a series of centrifuge tests were performed at 30 g on reinforced silty sand slopes of 2V:1H inclination representing 7.2 m height using a custom-designed rainfall simulator. The effect of geosynthetic type and optimum position of hybrid-geosynthetic layers within the slope were investigated. The slope movements, pore water pressure profiles, peak reinforcement strains and potential failure surface were analysed with the help of instrumentation and digital image analysis. The slope reinforced with geogrid indicated continuous build-up of positive pore water pressures during infiltration, while, the slope reinforced with hybrid-geosynthetic encountered lesser rise in phreatic levels by around 40% for the same intensity of rainfall. This resulted in substantially lesser peak strains of about 8% in the hybrid-geosynthetic layer as compared to the geogrids and non-woven geotextiles, wherein peak strain values as high as 48% and 19% respectively were registered. As far as the optimum placement of hybrid-geosynthetic inclusions within the slopes are concerned, the hybrid-geosynthetic layers placed within bottom one-third portion of the slope were more effective in drainage function. The hybrid-geosynthetic material thus developed can economize project costs by enhancing the performance of slopes with marginal soil deposits and the use of on-site local soils in reinforced earth construction.