Swell-consolidation characteristics of fibre-reinforced expansive soils

Many innovative foundation techniques have been devised to counteract the swell-shrink problems posed by expansive soils. Some of these techniques include physical alteration, sand cushioning, cohesive non-swelling soil (CNS) layers, belled piers, under-reamed piers, granular pile anchors and chemical stabilisation. Reinforcing expansive soils with randomly oriented geo-fibres is also an effective technique for controlling the volumetric changes in expansive soils. This paper presents the swell-consolidation characteristics of fibre-reinforced expansive soils. Nylon fibre was used to reinforce expansive soil specimens. One-dimensional swell-consolidation tests were conducted to study the swell-consolidation characteristics of fibre-reinforced clay specimens. The fibre content (fc) was varied at 0%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25% and 0.30% by the dry weight of the soil. The length (l) of the fibres was varied at 15 mm and 20 mm. The swell potential and the vertical swelling pressure decreased up to fc=0.25% for both fibre lengths, but increased mildly when fc was increased to 0.30%. The swell potential and the vertical swelling pressure decreased with an increasing fibre length (l) for all the fibre contents (fc). The rate of heave for the samples was also found to be in accordance with the above observations. The secondary consolidation characteristics of the fibre-reinforced samples were also studied and compared with those of an unreinforced specimen. It was found that the secondary consolidation characteristics of the fibre-reinforced specimens improved compared to those of the unreinforced specimen.