An experimental study of skin friction around piles in clay

Load tests on a model pile installed in Speswhite kaolin are described. The soil surrounding the pile was consolidated under a range of stress ratios K, and the pile was loaded under drained conditions in such a way that only shaft friction was generated. Pile installation techniques minimized soil disturbance so that the failure criterion for pile shaft friction could be investigated. The results, based on tests on nine normally consolidated and one overconsolidated sample, show that the angle of shaft friction is independent of the stress ratio in the soil before loading (0·7 <K <1·5), and is only justless than φ′triaxial for normally and overconsolidated kaolin. When loaded axially the lateral stresses on the pile shaft decrease with increasing shaft load for normally consolidated soil, and increase on loading in overconsolidated soil. Differences between adhesion factors α; back-calculated from the model tests and those normally encountered in practice highlight the effects of disturbance caused by mo...