Performance of Fiber Reinforced Fly Ash Mix as Infill Material in Geocell Reinforced Sand Bed

The large-scale generation and disposal of fly ash pose significant environmental concerns, highlighting the need for its sustainable reuse in geotechnical applications. This study investigates the performance of fly ash blended with polypropylene fiber as an infill material in geocell-reinforced sand beds to enhance bearing capacity and reduce settlement. Plate load tests were conducted in the laboratory by varying geocell mattress height, cement content, fiber content, and curing period. The results showed that polypropylene fibers improved the shear strength of the fly ash mix. Increasing the geocell mattress height from 0.5B to 1B enhanced the ultimate bearing pressure of a sand bed by 3.4×. At a mattress height of 1B, an improvement factor of 13.18 was achieved at a settlement (s/B) of 12.5%, and this improvement is attributed to confinement provided by the geocell because of enhanced load distribution. Fly ash mix with 6% polypropylene fiber and 5% cement yielded an ultimate bearing pressure of 460 kPa after 3 days of curing, which was 6.9× higher than that of an unreinforced sand bed. These findings demonstrate that fiber-reinforced fly ash is a sustainable and efficient infill material for geocell mattresses, offering both environmental benefits and improved geotechnical performance.