Plane strain capacity of a two-layered clay: Squeezing of upper layer

Mobile jack-up units operating offshore are generally supported by footings called spudcans. When installing a jack-up unit at a given location, geotechnical studies include assessments of the spudcan bearing capacity in order to determine spudcan penetration during installation and subsequent stability during operation. In layered soil conditions, a frequently used approach consists in considering simplified failure mechanisms in two-layer systems. This article studies the particular case of a soft clay layer overlying a rigid base, for which the failure mechanism involves lateral squeezing of the upper clay. Using computational limit analysis, as implemented in the software package LimitState:GEO, the plane strain squeezing bearing capacity factors are evaluated including the effects of foundation embedment and combined VH loading. Empirical analytical expressions are then adjusted on the numerical results to provide accurate estimates of the bearing capacity.