Thesis abstract:

This research is primarily concerned with the design and performance of piled foundations in expansive soils that develop desiccation cracks as the soil dries out. Because of uncertainties in the pile-soil interaction as the soil shrinks and swells the conventional response to this situation is to drive piles deep into the ground which has the benefit of minimising foundation movements caused by the seasonal soil movements. However, when the depth of soil affected by the seasonal changes is large this can lead to a requirement for long and costly piles with load capacities much greater than required. Recently, the design of foundations for wind and solar farms has led to reconsideration of the need for long piles. This is because a typical solar farm involves many thousands of short pile anchors and up to 100,000 for a large site, and they are often sited in arid regions where expansive soils are encountered. However, to be economic these piles need to be relatively short (typically 2 to 4 m), and thus penetrate less than the depth of the active zone, where seasonal changes of moisture occur, and within which cracks can develop in the drying soil. The crux of the research is hence to understand the unsaturated behaviour of expansive soil and behaviour of short piles.