Shaft Friction of Piles in Carbonate Soils

The paper describes the results of an investigation into the behaviour of friction piles in carbonate soils prompted by problems at the North Rankin site, and following on from work by Coop (1990) on the fundamental mechanics of these soils. Firstly a series of shear box tests was conducted which was aimed at examining the behaviour of the soil at the pile interface. These were followed by a short series of triaxial tests which confirmed that the mechanics of the soils were qualitatively similar to those tested by Coop. The in situ states of the Rankin soils were then examined within a critical state framework, correlating the soil state at any particular depth with published pile test data for the site. It is suggested that the flexibility of the pile may be an important influence on the capacity of steel piles. This may be the result of progressive failure, as the steel interface shear box tests revealed brittle strain softening behaviour.