Wind, wave and current forces cause significant overturning loads to be transmitted to foundation systems of fixed-bottom offshore structures, while buoyancy forces, in conjunction with environmental loading, impart direct tensile loads to foundations of floating facilities. Shallow skirted foundations are a potentially attractive foundation solution when overturning or tension loading is significant, as suctions mobilised within the soil plug provide tensile resistance. While passive suctions are maintained, undrained reverse end bearing will govern failure providing enhanced uplift resistance compared with vented pull-out of the foundation unit (with or without the soil plug), governed by skirt/soil friction. Currently uncertainty exists over the limiting ratio of skirt depth to foundation diameter to mobilise undrained reverse end bearing and the duration over which passive suctions can be sustained. This paper reports results from beam centrifuge tests investigating the response of shallow skirted foundations in lightly over-consolidated clay to concentric transient and sustained uplift.

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Environmental and buoyancy forces impart overturning moments and potentially direct uplift to offshore foundation systems. Shallow skirted foundations are an attractive design solution, as negative excess pore pressures developed within the soil plug provide temporary uplift resistance. This paper presents the results of beam centrifuge tests on a shallow skirted foundation in a lightly overconsolidated clay under eccentric transient and sustained uplift. When compared with the response under concentric uplift, the experimental results show a reduction in capacity and an increase in the rate of degradation of capacity under sustained loading.

Cet article présente une synthèse des résultats de l’enquête internationale sur l’état de l’art et l’état de la pratique en ingénierie géotechnique lancée par le Groupe présidentiel des entreprises associées et le Comité de supervision technique de la Société internationale de mécanique des sols et de géotechnique en mars 2017. Il résume également les discussions qui ont eu lieu sur le sujet durant le 19e CIMSG à Séoul, le 20 septembre 2017.