Upper bound solutions of vertical bearing capacity of skirted mudmat in sand

The mudmat is an important foundation form for deep water oil and gas engineering in the sub sea production system. The mudmat has a wide application prospective because of its shallower buried depth and convenient construction in the ocean. The existence of skirts, which are set up at the bottom of the mudmat in order to adapt to the requirements of the foundation slip resistance, increases the difficulty in the vertical bearing capacity calculation of the mudmat. The mudmat is simplified to a skirted strip foundation in this paper, and the mechanisms have been proposed according to the surcharge soil assumption. The upper value of the vertical bearing capacity of the mudmat is obtained by the upper bound theorem of the limit analysis. The soil damage rate as a new empirical parameter concerning the combined action between the skirts and the inner soil of the foundation has been defined. The value of the soil damage rate indicates the range of soil failure. The relationship between the soil damage rate and the aspect ratio is determined for the mudmat using a two-dimensional simplified analysis. The relationship of the bearing capacity factors Nq and Nγ with the friction angle is also discussed under the different soil damage rates.