Vibrocorer/Rockdrill System
Parent Body: British Geological Survey (Natural Environment Research Council), Continental Shelf and Margins Programme, Murchison House, West Mains Road, Edinburgh, EH9 3LA.

Principal Functions
To obtain 6m sediment cores, or 5.5m cores from rock at outcrop or subcrop in water depths up to 2,000m.

Subsidiary Functions
Measurement of geotechnical parameters for sediments through monitoring of penetration rate.

General Details
The vibrocorer consists of a twin vibrator motor housed in a pressure vessel driving a core barrel of 102mm outside dia. with a vibration force of 6 tonnes at 50Hz. The standard system, weighing approximately 3.5 tonnes, uses a 6m barrel, but smaller units with correspondingly lighter frames are available. A base mounted winch on the vibrocorer, which provides up to 12 tonnes withdrawal force, enables full barrel retraction prior to recovery on the main lift wire. A penetrometer with a chart recorder and analogue display gives a precise measure of penetration rate and depth. The power requirement is 30kVA, 415V, 3 phase 50Hz. Samples are retrieved in a clear plastic liner tube of 83mm internal diameter. The system has been tested to depths in excess of 1,800m and is designed for use to 2,000m.

Specification
The rock drill is built within a modular steel structure identical to that of the vibrocorer. The sea bed system is electro-hydraulic and fully self contained. The power swivel is base-mounted and drives the hexagonal outer barrel at variable drilling speeds up to 600 rpm. Controlled water flushing is run while drilling and in situ retraction is achieved by a base mounted hydraulic winch achieving a possible 12 tonnes withdrawal force. The drill uses microprocessor control. Penetration, retraction and the status of all drilling functions are monitored and displayed. The rock core (TBW 44mm diameter) is recovered in the steel inner barrel of the twin wall barrel system and archived in 1m long sections. The system is designed for use to 2,000 m water depth.

Special Features
The system requires a support vessel, preferably equipped with dynamic positioning and A-frame or moonpool deployment. Technical support team required for mobilisation, deployment and operation.

Future Plans
Provision of a fully, heave compensated hoist winch. Integration of cone penetrometer as an additional tool within the system.

Availability
The facility is available to other bodies in both the private and public sector. There are no restrictions on the type of body that can apply to use the facility. The advance notice required when requesting time on the facility should be as long as possible since an appropriate vessel is necessary and must be chartered. Time is allocated to other users subject to availability.

Charging Basis
Published charging rates are available, but these could be subject to negotiation. There are no minimum or maximum hire periods, but it should be noted that mobilising a suitable vessel for less than five days would be unrealistic.

Contact Information
Mr Alister Skinner
Head of Marine Operations
British Geological Survey
2A Nivensknowe Road
Loanhead
Edinburgh
EH20 9AU
Telephone:  +44 (0)131 448 2700   Fax: +44 (0)131 448 2545
Email:         mailto:acsk@bgs.ac.uk