Lateral holding capacity of skirted foundations on a soft seafloor soil

When a piece of equipment is placed directly on the seafloor, it is often important that its position and orientation remain stable. Depending on its characteristics, the seafloor slope, soil properties and ocean currents, the item might slide. Of special interest is the lateral holding capacity of small foundations with a perimeter skirt and internal shear keys. When designing a skirted foundation, you must balance the number of shear keys with the force required to insert the keys into the seafloor. With more shear keys, there is typically more lateral holding capacity, but also more insertion and recovery force, which can be a negative. The current tools used to design skirted foundations, in regard to lateral holding capacity, were developed by the oil industry for relatively large foundations with shear keys that penetrated several meters into the seafloor. The foundation size of interest is relatively small with shear keys that penetrate only centimeters into the seafloor. Given the drastic size difference between what the design tools were developed for and the size of the foundations of interest, laboratory testing of small shear keys was required to validate the design methods and potentially aid in modifying them. This paper will discuss the design tools for skirted foundations and the validation tests of these design tools in soft clay.