Abstract
The paper describes how research into the effective stresses developed on displacement piles has led to a new design procedure for driven piles in clay. The new approach calculates local shaft friction capacity from a failure criterion derived from (i) drained interface shear tests, combined with (ii) expressions which link the radial effective stresses at failure to the initial vertical effective stress (σ'vo), the apparent overconsolidation ratio (or YSR), the clay's sensitivity (St) and the relative depth to the pile tip (h/R*). Base resistance may be assessed by conventional methods, or estimated from a new relationship involving the local average CPT resistance, qc. The new method is demonstrated and verified using data from two Japanese case histories involving tests on large instrumented driven pipe-piles.
