SOIL DEFORMATIONS DUE TO CYCLIC LOADS ON OFFSHORE STRUCTURES

The type of offshore structure that may safely and economically be installed at a given site depends to a large extent on the local soil conditions. Fixed offshore structures may be grouped into three classes; pile supported, gravity and anchored. During the last few years large concrete gravity platforms have been used as alternatives to the more conventional piled steel structues at several locations in the North Sea. There are great difficulties encountered in performing high quality soil investigations offshore due to deep waters, restless seas and lack of well suited and calibrated sounding and sampling techniques. The foundation soil behaviour has to be analyzed for large cyclic loads superimposed on the static ones. Experimental results from soil elements subjected to cyclic loads in the laboratory show substantial scatter, which gives rise to large uncertainties in the analytical predictions of field performance. Very recently one has gained experience and recorded data from the crucial installation phase and the later performance of gravity platforms in the North Sea. A systematic evaluation of the reliability of present practice and available engineering analyses has started by comparing before-the-event predictions to field measurements. It is attempted to give an overview of the geotechnical engineering performed for offshore gravity structures and to point out to what extent theories of probability and statistics so far have been used. Specific cases are considered for probabilistic analyses of the platform installation phase and foundation stability during storm loading.

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  • Corporate Authors:

    Norwegian Geotechnical Institute

    P.O. Box 40 Tasen
    Oslo 8,   Norway 
  • Authors:
    • Andersen, K H
    • Hansteen, O E
    • Hoeg, K
    • PREVOST, J H
  • Publication Date: 1978

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  • Accession Number: 00185110
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 3 1979 12:00AM