Driveability Analysis Techniques for Offshore Pile Installations

Pile driveability analyses for offshore platforms require a unique set of criteria, which may not normally be associated with other pile foundation installations. The selected hammers, pile makeup details and soil profile must be carefully reviewed, as these factors will determine if pile installations will be successful. The most important of the variables to establish is the expected Soil Resistance to Driving (SRD). Common practice is to relate the SRD to the Static Soil Resistance (SSR) which is normally provided based upon the American Petroleum Institute (API) methods of calculation or some variance based upon local site conditions and experience. In addition, due to the substantial use of hydraulic hammers hammer operating energies must be selected such that pile driving can be accomplished while avoiding pile damage. Current procedures used for driveability analysis will be provided and the methods of parameter selection discussed in detail. These procedures, which have been used on several offshore projects in various offshore fields around the world, will be presented with the original driveability analysis and the recorded pile installation records. A method to determine the expected SRD will be discussed based upon the experience collected from these sites which are in numerous offshore fields worldwide. Four Case Studies are shown to validate the described methodology.