Sediment vibrocoring

Brief description


Vibrocorers are used wherever soil conditions are unsuited to gravity corers or where greater penetration of the seabed is necessary. There are a number of types, such as the Quaternary Resources SEAS* (*Submersible Equipment and Services) vibracorers and the Aimers McLean type, which are standard industry designs for use in sands and denser/stronger soils. It is the next step down from the rotary rock corer. Vibrocorers are used widely throughout the geotechnical investigation industry and can be deployed in water depths up to 1,000m.

See NOAA's summary table at summary view of sediment vibrocoring technique (144 KB PDF).

 

 

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Vibracoring

The vibracoring technique provides a more reliable means to sample unconsolidated and semi-consolidated sediment sequences by means of a submersible, electrically powered, vibrating head attached to a rigid core barrel (normally aluminium, 76mm ID, 80mm OD) that by its agitation forces the core barrel to be driven into the seabed.

The Vibrator Unit      Assembled Vibracorer

The entire coring process, including deployment and recovery of the drilling rig, is around 30 minutes depending on the water depth and deployment configuration. The vibracorer can be deployed and recovered in a number of different ways depending on the configuration of the drilling platform (e.g. A-frame, hydraulic crane, Hiab, etc). Strong rope (c. 25mm) or steel cable (c. 10-15mm) with a rated lifting capacity of a least 2 tonnes is required for the lifting of the corer from the vessel deck or from the seabed during deployment and recovery.

Upon recovery, core samples can be analysed on-site, or stored for later examination. The aluminium core barrels can be easily cut to the length of the recovered core to enable capping and transport if required. Alternatively, the barrels can be cut lengthwise to slab the sample for on-site examination.

Examples of stratigraphic cross sections of the seabed showing vibracore data incorporated 
with seismic and bathymetric survey data.

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