Axial cyclic loading of piles in low to medium density chalk

Comprehensive field investigations into the axial cyclic loading behaviour of open-steel pipe piles driven and aged in low-to-medium density chalk identify conditions under which is stable, unstable or metastable. Post-cycling monotonic tests confirmed that stable cycling enhanced pile capacity marginally, while cases suffered potentially large losses shaft capacity. Metastable led to intermediate outcomes. The patterns by deflections grew varied systematically with normalised parameters could be captured simple fitting expressions. Cyclic stiffnesses also conditions, highest operational shear falling far below in-situ seismic test values. responses were controlled of, within, reconsolidated, de-structured, putty annuli formed around shafts during driving. Fibre-optic strain gauges identified progressive failure from tip upwards. Large factors safety required for survive repetitive high-level, two-way, involving low mean loads, amplitude one-way had little impact. A ‘global’ prediction procedure employing interface triaxial shown provide broadly representative predictions behaviour.