The Performance of Fly Ash as Fill Material for Embankment Model on Soft Soil

Fly ash is one of coal ashes resulted from power plants using coal to generate electricity. As a result of large utilization of coal, large volumes of coal ash produced as waste material. Direct use of these materials in construction projects, not only provides a promising solution to the disposal problem, but also as an alternative for structural fills material. High shear strength, low compressibility and permeability, self-hardening with time and relatively lightweight make the material suitable as a replacement for fill materials in embankment construction. This paper investigates the performance of fly ash as fill material for embankment model constructed on soft soil and hard soil foundation by means of small geotechnical centrifuge and finite element analyzed. For comparison purposes, embankments using residual soil as fill materials were also tested. The results from centrifuge modelling and finite element analysis showed that the use of fly ash as fill material for embankment on hard soil give a tremendous effect in terms of decreased settlement and increased in height of prototype, factor of safety and time of failure, compared to the residual soil embankment. Settlement was reduced by about 130% if fly ash embankment (28 days curing time) constructed on hard soil was compared to residual soil embankment. However, for fly ash and residual soil embankments on soft soil, the main problem was excessive settlement of embankment and foundation. The paper concludes that fly ash is very promising as fill material for embankment construction.