Tensile shaft capacity of bored piles in sand from centrifuge modelling

摘要

In the current design practice the evaluation of the skin friction developed on piles shaft in sand is obtained using the "β method", which accounts, implicitly, for a number of factors, controlling the magnitude of the ultimate shaft friction, τ_(su), specifically: the initial state of the sand, its modification caused by pile installation, the soil shear strength and the roughness of the pile-soil interface. To analyse the friction interface behaviour, avoiding the effect of the base resistance, a series of 32 pull-out centrifuge tests have been performed, from which the β coefficients were determined and compared to those estimated from back analysis of loading tests on full scale piles. The β vs. depth profile gathered from centrifuge tests in dense sand was explained by the increment of the radial stresses on the pile shaft occurred during loading.