May/June 2021 - 107

BRIAN S. WOOD, PARTNER,
SMITH CURRIE
LEGALLY SPEAKING
Limiting Marine Project
Geotechnical-Related Claims
Marine construction projects present
particular, and sometimes unique,
challenges for geotechnical design and
construction. These issues extend from
early on to project completion. Some
challenges are that:
* Marine project sites are generally
environmentally sensitive and
often involve a complicated,
lengthy permitting process.
* Investigations of the seabed and
below are generally more
expensive and time consuming
than onshore geotechnical ones.
* Designs of marine structures must
account for significant lateral
loads, cyclic loading and a wide
range of environmental and
geohazard elements (wave action,
scour, submarine landslides, etc.).
* Construction of deep foundations
and ground improvement elements
on or under a seabed generally
costs more than onshore
foundation construction.
* Environmental considerations can
limit the amount of disturbance of
the seabed and preclude
construction during certain
periods.
* Inclement weather is often more
severe and impactful on marine
construction activities.
* Design modifications during
construction can be very costly to
implement/construct.
These challenges can translate into cost
and schedule overruns. A January 2004
study in Transport Reviews (and
subsequent updates) conducted by
Professor Bent Flyvberg at Oxford
University revealed that bridge and
tunnel projects go over budget by an
average of 34 percent.
Marine Geotech Claims
Where there are cost and schedule
overruns, there are construction claims.
Many arise from foundation and other
geotechnical-related issues. A survey of
bridge project-related claims was done
of State Department of Transportation
engineers and engineering consultants.
Published in May 2020 (Pramen et al.,
Journal of Legal Affairs and Dispute Resolution
in Engineering and Construction),
it found that four of the top five
geotechnical-related causes of claims
on bridge projects were due to:
* An insufficient number of boring
locations
* A misclassified or
mischaracterized subgrade
* Inadequate specifications for piling
* Changes in piling quantities due to
selecting the wrong pile type for a
particular soil type
Mitigation Approaches
The engineers and consultants surveyed
also recommended ways to mitigate the
cost and schedule overruns attributable
to geotechnical-related causes. The top
five recommendations were that:
* Bridge designers should have
detailed knowledge about
geotechnical information of the
project site.
* Detailed site investigations should
be performed by experienced
geotechnical consultants.
* Standardized minimum standards
for subsurface investigations and
site characterization should be
developed.
* More attention should be paid to
the selection of pile types and
prediction of pile lengths.
* Boring locations should be selected
more accurately.
The survey further revealed that
standard penetration tests (SPTs) are by
far the most common and preferred
subsurface investigation method for
bridge projects, followed by cone
penetration tests (CPTs) and geophysical
methods. For large marine projects, it is
common for site investigations to
include a combination of sampled
bor ings , CPTs and geophys i ca l
investigation methods.
Among the geophysical methods
commonly used for sub-bot tom
stratigraphy are acoustic-based
systems, such as single-beam and
multibeam echo-sounders. Specific
tools used to collect sub-bottom data
are boomers, sparkers, pingers and
chippers. The tools have varying
abilities to penetrate the seabed and
identify sub-bottom features. While the
specific technologies differ, each emits
an acoustic signal that passes through
different materials (such as sands,
clays, mud) and measures the time and
intensity of the energy reflected back to
a receiver. The acoustic impedance of a
material correlates to that material's
density. The intensity of the returning
signal and the time the signal takes to
return gives useful information about
how thick the sediment strata are at a
given location and the location and
DEEP FOUNDATIONS * MAY/JUNE 2021 * 107
May/June 2021

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