Piled footings – an alternative foundation system in expansive soils

The use of piled footings and lining panels in expansive soils was explored through detailed field studies carried out at a site near the north boundary of the National Institute of Technology, Warangal campus in India and also on the tail channel of Kakatiya canal at 257·902 km from the Sriram Sagar Project. The heave measurements were made for the consecutive four seasons of cyclic wetting and drying. From this study, it was found that the piled footings and lining panels have shown a marked decrease in heave, indicating their promising performance in swelling clays. Pile pullout tests were also carried out in the field to calculate the resisting force against the uplift load on the footings. The uplift load on footings was estimated based on the field swell pressure value of 210 kPa. It was also revealed that the heave is significantly decreased despite the wide gap between the uplift and resisting forces that was perhaps due to the sensitivity of heave to initial restraint offered by the pile shaft resistance. Two case studies, for which the proposed system of piled footings was used, are also included in this paper. These structures were observed to be crack free for the past 4 to 5 years and proved the merit of the technique.