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Copy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

PIPELINE STABILISATION USING PRE-TRENCHING AND SAND BACKFILL

ABSTRACT Stabilizing large diameter natural gas pipelines on the seabed against extreme hydrodynamic loading conditions has proven to be challenging in the northwest of Australia. Tropical storms, which affect the area annually between November and April, can generate wave heights exceeding 30 m and onbottom steady-state currents of 2 m/s or more. Consequently, in shallow water depths, typically less than 40 -60 m, subsea pipelines can experience very high hydrodynamic loads, potentially causing significant lateral movement. If the seabed is rugged, or at locations where the pipeline approaches a point of fixity, this can lead to the pipeline suffering mechanical damage, which is undesirable

CSi—a joint industry project into CPTUs in silty soils

The CPTU constitutes the main in situ offshore investigation tool for geotechnical site characterisation and provision of soil input for the design of wind turbine foundations. CPTUs are typically performed at all foundation positions. Thus, all obtained results of supporting geotechnical in situ, model and laboratory testing need to be confidently correlated to the CPTU parameters. Most of the interpretation methodologies available for industry practice consider the soil behaviour around the cone either as fully drained or undrained, and acknowledged and well-proven correlations between CPTU parameters and classification and engineering properties exist for sand and clay. However, for transitional soils, e.g. silty soils, which may exhibit partial drainage during standardized cone penetration, such robust interpretation schemes do not exist. This paper presents the background, the objectives, setup and early field results of a joint industry project into CPTUs in silty soils for developing schemes for planning, execution and interpretation