Seabed sampling

 

Vibrocore

The electric twin-linear vibrocorer has a modular frame construction allowing for the recovery of 4-, 5- and 6-meter continuous 86mm diameter samples in water depths of up to 200 meters. This approach is used for obtaining cores in most marine sediments ranging from silt and sand to gravel and stiff clay. The recovered samples are suitable for further geotechnical lab testing and analysis.

 

Piston (gravity) corer

A stationary piston corer is basically a gravity corer dropped freefall from a predetermined height using a trigger system. It contains a fixed piston that remains stationary as the core barrel penetrates, thus creating a negative pressure in the coring tube. This technique generally results in improved recovery rates compared to those obtained with a standard gravity corer, particularly in soft soils. The piston assembly uses variable core barrel length (3 -12m) and is able to obtain continuous 86mm-diameter core samples in water depths from 10 – 2000 meters.

 

Grab and box seabed sampling

In addition to cone penetration testing and comprehensive core sampling capabilities, UTEC routinely provides grab-sampling services, which can be particularly valuable in shallow waters for environmental work.

A box corer is a large mechanical coring device containing a box that takes a large, relatively undisturbed sample when lowered to the seafloor by a wire from the work platform. The box corer is pushed into the sediment by its own weight. When the deployment line is retracted, a rotating spade closes off the bottom of the box before the box corer is lifted.

 

ROV push cores

Depending upon conditions, ROV push samplers can be used with Shelby tubes to acquire samples from the seafloor to 1.5 meters. This sampling device is operable by the manipulator arms on remotely operated vehicles (ROV). Generally, ROV-operated samplers obtain fairly short, small-diameter cores, intended for use in deep water.

 

Offshore laboratories

Following successful acquisition, samples are then routinely collected, documented, tested and stored onboard the vessel in dedicated functional, container-based laboratories.

Offshore sample testing includes:

• Core logging
• Classification
• Photography
• Atterberg limits
• Pocket torvane
• MiniVane
• Moisture content
• Bulk density