In recent years there has been a large increase in offshore oil and gas exploration activities. A large proportion of the work is being performed with jack-up drilling rigs.
Jack-up rigs basically are of 2 types, depending on their foundation:
Individual footings (spud cans).
Mat supported rigs have a large foundation bearing area and therefore impose relatively low bearing pressures on the seabed resulting in limited penetration. Mats are usually A-shaped and are suitable for use when the seabed comprises very soft clay soils. However, mat supported rigs require that the seabed is fairly level and their stability is sensitive to factors such as subsoil variability, cyclic and eccentric load effects, lateral sliding resistance and seabed instability. Rigs supported on individual footings are more numerous and much more widely used in South East Asia and this paper presents aspects of geotechnical hazards that may be encountered when their legs penetrate into the seabed.