September/October 2022 - 113

waves. The team identified sand waves
that are locally higher than 10 m (328 ft)
between crest and trough. This form of
seabed features will create significant
issues for cable installation, burial and
long-term maintenance.
It is not just the specific surveys that
early-stage decision making and
advance project definition. However,
this information would not be of
sufficient resolution to identify local
geohazards or seabed features. In one
example, an image can show the
bathymetry for the same part of the
seabed using two different surveys,
with high-resolution MBES data
Conceptual ground model
* Developed from Desk Studies and
opportunistic datasets.
* Used to identify data gaps,
potential hazards, general geology,
etc.
* Initial identification of constraints
such as pipelines and cable routes.
* Used to target first site-specific
G&G surveys.
* Usually contains limited or no
subsurface data...
allowing a ship wreck to be clearly
identified, whereas another may not
have sufficient resolution.
In another example of highresolution
bathymetric surveys, related
to a recent research project in the Irish
Sea, publicly available MBES data were
used to characterize mobile bedforms
and, in particular, to characterize sand
Preliminary/recon ground
model
* Developed from reconnaissance
survey data (always geophysical
and hydrographic data, commonly
geotechnical data).
* Not usually full coverage - grid or
corridor pattern.
* General geological units.
* General depth to bedrock.
* Indicative geotechnical
parameters.
* Up-to-date water depths
(bathymetry).
Opportunistic
datasets
Preliminary/
recon survey
* Indicative obstruction density
* Used to target infill/full coverage
G&G surveys.
Infill/full site
survey
Typical ground model development stages
DEEP FOUNDATIONS * SEPT/OCT 2022 * 113
Locationspecific
survey
need to be chosen but the acquisition
parameters are also as important. There
is nearly always a trade off as a higher
resolution of the data usually comes
with the detriment of spatial and vertical
coverage and additional expense.
The survey strategy should seek to
address the balance between budget,
coverage and resolution at different
stages of the project. It is also worth
mentioning that increased data
volumes result in increased acquisition
and processing durations, so the project
schedule is also a key input to the survey
strategy. There is an interrelationship
between the survey strategy and the
ground model. The survey strategy
defines what data you get and when.
The ground model is where you put the
data once acquired. The conceptual
ground model feeds into the survey
strategy document, and that is where
you define (based on a gap analysis) the
surveys you will need to meet the needs
of the design milestones and the
policies, standards and requirements
needed to achieve your auction,
exclusivity and planning permissions.
Full ground model
* May have multiple iterations.
* Detailed geological units.
* Detailed depth to bedrock.
* Full geotechnical parameters.
* As-found infrastructure mapping.
* Up-to-date obstruction mapping.
* Up-to-date bathymetry.
* Soil zonation.
* Location-specific data.
September/October 2022

Table of Contents for the Digital Edition of September/October 2022
