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Re-visiting Yolla - Managing Jack-up Storm Stability; Geotechnical Assessment

In 2004 the Ensco 102 was spudded alongside the Yolla A platform in the Bass Strait, Australia.

01 Sep 2015
Amodio, A., Erbrich, C., Murugavel, V. and Moyle, I.


The uncemented silty carbonate soils at this site required a modified approach to documenting stability during storm events as discussed in Ref [1]. In early 2015 the Seadrill West Telesto was brought alongside the Yolla A platform with its spudcans repenetrated deeply through the remoulded infill material within the existing craters. An extensive engineering exercise was commissioned to assess the storm stability for this new rig which involved a complex interaction between soil consolidation times and strength degradation under cyclic loads, coupled with uncertainty as to exactly what depth each of the spudcans would end up and hence what soil type they would rest on. A variety of anticipated scenarios were assessed, which included the effect of varying the installation preload, varying the return period of the storm and varying the VDL as a function of time. This paper will present the geotechnical work undertaken to unravel this complex puzzle, which led to a detailed installation flowchart that provided guidance on the process required to meet the acceptability criteria for each leg.


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