Method for predicting foundation stability for equipment placed on grade in a seafloor environment

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 and the seafloor soil properties, the item might slide, tilt or settle excessively. The analytical tools currently available in geotechnical engineering practice do not fully address the behavior of such an object in the seafloor environment, especially regarding the unusually soft and varied surface soils commonly found there. A method was developed to predict this behavior. It incorporates elastic and plastic (bearing capacity failure) soil deformations, and includes accounting for a varying soil shear strength profile. It requires only knowledge of the shear strength profile, using an approximation for the soil´s elastic modulus that was developed from published data. Results appear reasonable, but remain to be confirmed by comparisons with actual observations. The method is particularly useful for predicting the tilting stability of items placed on a very soft surface layer overlying stronger deeper layers.