Lightweight recycled geomaterials reinforced with geogrids

Scrap tyres are unwanted urban waste, the volume of which is increasing every year. One possible recycling method is for the shredded tyres, either alone or mixed with soil, to be used as a lightweight geomaterial. The present study aimed to examine (a) the interactions between geogrids and a tyre chips–sand mixture, (b) the performance of a full-scale geogrid-reinforced test embankment and (c) a numerical simulation of this full-scale test embankment. Numerous experiments were performed in the laboratory to investigate the interactions between the geogrid and the tyre chips–sand mixture. A full-scale, geogrid-reinforced embankment with lightweight tyre chips–sand fill was then constructed on soft Bangkok clay and extensively instrumented to evaluate its performance. The unit weight of rubber tyre chip–sand mixtures with ratio 30:70 per cent by weight was 13·6 kN/m³ compared with 18·0 kN/m³ for conventional sand backfill. The total settlement magnitude of 122 mm of the lightweight embankment was 67·5% less when compared with the corresponding value of 400 mm for conventional embankment. Numerical analysis using two-dimensional plane strain conditions provided satisfactory predictions for the full-scale field test.