Lateral boundary effects in centrifuge foundation tests

Large deformation finite-element analyses were conducted to explore the effect of the container lateral boundary in centrifuge tests where a large offshore foundation is tested. A spudcan foundation, typically used to support jack-up drilling rigs, was penetrated into uniform clay, uniform sand and sand overlying clay stratigraphies under rough and smooth lateral boundary conditions. The effect that the proximity of the container lateral boundary has on the measured load–penetration response is quantified. The boundary impact varies with the soil profile and boundary roughness, and for sand-only or sand-over-clay conditions the required separation between the foundation and the container boundary is far greater than in clay-only conditions. In most cases, during large penetration of the spudcan foundation, the largest influence from the lateral boundary was on peak resistance, and diminished during the subsequent deeper penetration. For practical use, a centrifuge container design chart is proposed to check whether the dimensions are adequate for the foundation and model size to be used in an experiment. It is shown that the results from many earlier studies could have been potentially influenced by container boundary effects.