Behavior of expansive soils under stabilized fly ash cushions during cyclic wetting and drying

Structures built in expansive clays are likely to be damaged due to the strains caused in them by alternate swelling and shrinkage. Variations in the moisture regime during monsoon and summer are the cause of this alternate swelling and shrinkage. Several innovative foundation techniques have been suggested to overcome the problems associated with expansive soils. Belled pier and under-reamed pile are some of the foundation practices adopted in these soils. Besides, overburden in the form of a sand cushion or a cohesive non-swelling soil (CNS) cushion has also been tried for arresting heave. But, most of them suffer from one shortcoming or the other. In order to overcome the drawbacks of the existing foundation practices, fly ash cushion, stabilized with lime or cement, has been tried by the authors. The principle of this technique is the same as that of a CNS cushion. This proved to be very effective in arresting heave. However, its efficacy over a few cycles of wetting and drying needs to be established since CNS cushion, which was found to be effective in arresting heave during the first cycle of wetting and drying was ineffective during the subsequent cycles. The present study relates to the behavior of expansive clays under lime- or cement-stabilized fly ash cushion subjected to several wetting and drying cycles.