Arkutun Dagi Geotechnical Survey

An offshore geotechnical investigation program was initiated by Exxon Neftegas Ltd. for a concrete gravity-based structure (GBS) platform and a pipeline corridor at the Arkutun Dagi site, offshore Sakhalin Island.  The site is located on the northeastern shelf of Sakhalin Island in about 35 m of water.  The dimensions of the proposed GBS platform to be installed are about 100 m by 100 m.  The associated pipeline corridor is about 25 km long.   The site investigation program consisted of drilling and sampling of a number of geotechnical boreholes, CPT soundings, grab samples and laboratory testing.

In 2007, the site investigation contract was awarded to Pacific Engineering Company Limited (PECO), who contracted M+EG to provide QA/QC services to the site investigation program.

• Supervise all technical aspects of the field activities.
• Provide QA/QC services on the drilling vessel and in the offshore laboratory.
• Review field data and perform preliminary soil characterization.
• Prepare testing logs and site investigation report
• Review and interpret onshore laboratory testing results, including advanced dynamic testing, to define engineering parameters to be used for design.

• The presence of a 7-m thick cohesive layer at about 10 to 15 m depth was considered critical to the foundation response.  Assistance and recommendations were provided to PECO during testing and sampling to optimize the amount of data to be retrieved to characterize the cohesive layer.
• Soils encountered at the site consist of very dense sand.  Refusals were often encountered during sampling as the Shelby tube could not penetrate the soils sufficiently.  Recommendations were provided to PECO to modify the sampling procedure to improve sample recovery, in order to meet the specification.
• Interpretation was carried out for the cyclic triaxial tests.  The results were compared with published data to define the dynamic properties.