An investigation of the behaviour of bored piles in pyroclastic sands

Much of the area to the east of Naples, Italy, is covered by sands of pyroolastic origin. The in situ states of these soils are very variable but are often loose and the particles which constitute them are, by nature, usually crushable. The soils therefore tend to be more compressible than more commonly encountered sands such as those of siliceous mineralogy, which has led to problems with foundation settlements even when piles are used. The paper describes results of laboratory tests investigating the mechanics of these sands, highlighting similarities with other crushable soils and the consistency of this behaviour within a general framework applying to all sands. The paper then presents the results of load tests carried out on two instrumented bored piles, examining their behaviour within the context of a fundamental understanding of the mechanics of the soils. Just as the mechanics of the soils is consistent with that of other crushable sands, the underlying behaviour of the piles is also similar.