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Zawartość zarchiwizowana w dniu 2022-12-27

CLASSIFICATION OF SEA FLOOR ENGINEERING PROPERTIES FOR MARINE FOUNDATIONS AND STRUCTURES

Cel

The main objective of this project is to investigate the interrelationships between acoustic reflections from the seabed measured with an Ultrasonic Signal Processor, with in-situ values determined from a seabed instrument sled. A successful conclusion to the project will enable compilation of a classification table of results determined from analysis of acoustic reflections. This will enable engineering properties and stability of the sea floor to be directly inferred, such that more rapid and cheaper surveys of areas can be achieved using acoustic methods.
The Sea Floor Probe itself may prove to be an innovative method of in-situ measurement of foundation engineering properties. However, the successful development of USP will revolutionise shallow geophysics and the results presently obtained which are to an extent based on the individual interpretation by the geologist/geophysicist.
Site and platform design engineers require precise information of the seafloor characteristics at the earliest stages of development to assess site suitability and to input into structural designs. Similarly, resource managers of all kinds operating in the offshore environment are employing increasingly sophisticated models in their search for viable propositions.
To this end Irish Hydrodata Limited have combined their efforts with Auger Geophysical Services, Micro Marine (Systems) Limited and the University of Surrey to develop new techniques applicable to the offshore survey industry.
By bringing together geophysical, electronic engineers, engineeringgeologists, geologists, and oceanographers and physicists, the aim was to develop methods for the rapid quantification of the seafloor sediment properties, using the opportunity of an integrated testing programme to compare individual systems and ultimately enhance data acquisition.
USP
A survey version of the original fishing USP model has been produced which can quantify the type of sea-bed underneath the vessel using the ships echosounder.
USP technology currently requires extensive ground truthing to calibrate its output which is variable dependent on such factors as :
- Echosounder frequency, pulse width, transducer type, mounting on hull, etc.
- Vessel's hull shape (especially in shallow water)
- Background acoustic level (ship's engine, etc)
- Water temperature and salinity.
Ideally, USP output should be capable of being supplied in a wholly standardised format to be deployed on 'Craft of Opportunity' with minimal, if any, calibration. A parallel receiver to be developed in the project extension will qchieve all expected aims.
Sledge
The sea floor sledge is the first pseudo-underway profiling system capable of measuring both seismic body wave velocities as well as formation factor. As such it represents a major advancement in geophysical measurement facilities available to the marine scientist. Its potential lies in that it is able to provide sediment data remotely and for the in-situ condition, and that it can collect this information more rapidly and economically than any other currently available technique.
Although now a working system, a number of potential improvements have been identified which would convert the instrument package into a commercially viable tool. These include some innovative developments e.g. simultaneous measurement of focused and unfocused resistivity to provide a depth variation in apparent formation factor, shear wave source design modifications to remove pre-pulse effects and whole wave form analysis of seismic data.
The project is designed to follow a six phase operation :
Phase 1
- Development of Sea Floor Probe
Development of survey version of USP
Conventionql surveys of test bad areas off Cork:North Wales
Phase 2
- Joint initial trials of probe, USP and conventional instrumentation
Phase 3
- Redevelopment of work in probe
Redevelopment of work USP
Further conventional surveys of test bad areas off Cork/North Sea Wales.
Phase 4
- Joint trials, marine ground truthing and surveys, using USP probe
and conventional instrumentation including coring:grab sampling
Phase 5
- Data analysis of USP results
Laboratory testing and comparison of probe results
Analysis of conventional survey results for cahacterisation and control
of sediment distribution in test-bad areas
Mechanical testing of core samples for static date
Phase 1-5
- Mathematical analusis and numerical modelling of acoustic wave theory
Phase 6 - Reporting
The joint Irish/British project will involve three main subcontractors :
- Micro Marine (system) Limited
CORK
- Augur Geophysical Services
University College of Worth Wales
ANGLESEY
- Dr R.C. Chivers
University of Surrey
GUILFORD

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Koordynator

IRISH HYDRODATA LTD
Wkład UE
Brak danych
Adres
RATHMACULLIG WEST BALLYGARVAN
CO. Cork
Irlandia

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