Vertically loaded shallow foundation on soft clayey silt

This paper presents the results from a field experiment involving the vertical loading to ultimate failure of a shallow pad footing founded on a soft estuarine clayey silt. Data from settlement plates and pneumatic piezometers located beneath the footing are used, in conjunction with estimated stress distributions, to compare the ground's stiffness characteristics with those measured in laboratory tests. The operational undrained shear strength of the clayey silt, inferred from the ultimate vertical load of the foundation, is also compared with in situ and laboratory estimates of undrained shear strength and with operational strengths estimated from a similar footing test. The paper presents the results from a prediction competition held for the footing experiment with a view to assisting assessment of the reliability of standard design prediction procedures.