Field studies of an instrumented model pile in clay

An instrumented model pile was used to investigate the fundamental behaviour of driven cylindrical steel piles, in clay soils. Data are described from two test-bed sites, one with heavily over-consolidated clay, and one with normally consoli-dated clay. These confirm that a residual shear surface is formed adjacent to the pile shaft during installation. Comparisons with other site investigation data and cavity expansion theoretical predic- tions suggest that stress relief immediately behind the pile tip during installation gives rise to total radial stress and pore pressure measurements on the shaft which are lower than the simple cavity expansion model predicts. However, the data did indicate that the radial effective stress might be successfully predicted. During reconsolidation, the radial effective stress drops initially, followed by a slow recovery, which was insufticient in the two clays investigated for the final value to reach that during installation. On undrained loading, the clay adjacent to th...