Study on the Bearing Characteristics of Different Shaped Mats on Cohesive Soil

Abstract

Mat foundations have been widely used as foundations of mobile offshore platforms such as jack-up rigs and installation platforms. Throughout the service period, the mat bears coupled multi-dimensional loads transferred from the superstructure and directly from the environment. Evaluating the bearing capacity of the mat is the premise of offshore platform design. However, there are few studies on the bearing capacity of commonly used irregularly shaped mats under multi-dimensional load conditions. Looking at two types of A-shaped mats on cohesive soil, uniaxial bearing capacities are calculated using the finite element method (FEM) in this study. The centrifuge test was performed to verify the FEM results. Effects of the length-to-width aspect ratio of the foundation on bearing capacities are discussed. The V-H, V-M, and V-H-M failure envelopes of mats with unlimited and zero tension interfaces are obtained. Studies have shown that the uniaxial bearing capacities change monotonously with aspect ratio increases, and that the bearing capacity of a rectangular A-shaped mat is higher than that of a trapezoidal A-shaped mat. The V-H-M envelope with unlimited tension interface condition is ellipsoid-shaped, while that with zero tension interface is scallop-shaped. With the capacity expressions established in the paper, it is possible to quickly check the bearing state of the mat under a given V-H-M load condition, and then assess the safety of the engineering operation.