Jack-Up Platforms

Design loads on a jack-up rig. (After McClelland, B. et at, Avoiding jack-up rig foundation failure. Symposium on Geotechnical Aspects of Off shore and Nearshore Structures, Bangkok, Thailand, A.A. Balkema, Rotterdam, the Netherlands, pp. 137-157,1983. Reprinted with permission from Geotechnical Aspects of Coastal and Offshore Structures, Copyright Taylor Francis Group.) 

The rig mover continues to jack the hull out of the water at 10 to 30 m per hour until an air gap of approximately 1.5 m is achieved (McClelland et al., 1983). The required air gap depends on the wave height. The rig mover then levels the platform before beginning preloading to achieve a final penetration of the legs. The legs are preloaded in steps by filling tanks in the platform with seawater. The maximum preload typically corresponds to the load the platform 

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This chapter is organized into sections on loadings, pile structures, gravity platforms, anchor uplift capacity, jack-up platforms, and hydraulic filled islands. 

The second step of computation takes into account the influence of the weaker layer on the bearing capacity of the hard layer. The computations are based on assumptions (l)-(4) using Meyerhof and Hanna s methods as described in Hanna and Meyerhof (1980) or Meyerhof and Hanna (1978), depending on the soil characteristics. Examples of prediction results for a jack-up platform operating in the Baltic Sea are presented in Figure 10.55. 

Wemo, M., Juszkiewicz-Bednarczyk, B., and Inerowicz, M. (1987), Penetration of jack-up platform footings into the seabed. Marine Geotechnology, 7, No.2, pp. 65-78. 

Jack-up platform working in exposed wave conditions in Sennen Cove (courtesy Seacore)... 

Figure 4.7. Jack-up platform collapsing. Investigation concluded that the jack-up leg possibly penetrated historical borehole (courtesy Tony Edmundson)...

Figure 5.13. Jack-up platform used for marine piling close inshore (courtesy Edmund Nuttall)...

Figure 5.14. View of jack-up platform. Note that different legislation applies to different parts of the platform, see also Figure 2.2 (courtesy Seacore)...

Figure 6.2. Example of a jack-up platform where different working areas...

One specialised marine contractCH stated that on its jack-up platform it tended to work in close knit small teams, who each know each other s roles, responsibilities and competencies. It believed that this working relationship helped manage health and safety. 

Life-jackets or buoyancy aids must be worn where there is a foreseeable risk of drowning when working on or near water and at all times while working on boats. Risk assessments can be used to identify areas which are safe and where no buoyancy equipment is required (e.g. accommodation blocks on a jack-up platform). Equally areas where there is a high risk should reinforce procedures. 

The four platforms consisted of a small wellhead platform called NA, a residential platform called MHF, the main processing platform called MHN, and a relatively new additional process platform called MHW. At the time of the accident, a further temporary ( jack-up ) platform called Noble CharUe Tester was alongside the complex working on the NA platform. 

For shallow water depths, drilling is preferably performed from a jack-up platform. See Figure B.IO. 

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