HYDROCARBON
ENGINEERING
18
The
importance
of geotechnical
investigations
Michelle Wagner, Bob Kruger, Rebecca Zackavec,
Marty Tellalian and Mark Butts, CB&I, USA,
emphasise
the importance of early and comprehensive geotechnical
investigations for LNG tanks.
A
s global demand for LNG
escalates, a critical component
of the rapidly expanding
infrastructure system is an
accurate and cost effective storage tank
design. A large contributing factor in both
the tank and foundation design is the site’s
soil and seismic conditions. As such, a
compelling argument can be made for a
deliberate and attentive approach to
geotechnical investigations. Done early in
the project development lifecycle, a
complete investigation can benefit both
owners and tank contractors. It is therefore
imperative that all stakeholders are aware
of what comprises a complete
investigation, when the investigation
should be performed, and how each entity
works together to create the tank and
foundation bid design. Understanding these
areas will highlight how fewer assumptions
during the bid process enables value based
engineering, allows for more accurate
schedule and cost estimates, and prepares
owners and project developers to make
informed decisions when evaluating and
selecting a tank contractor’s bid.
The role of
geotechnical
investigations
An in depth geotechnical investigation
focused directly beneath the tank footprint
provides essential information, ultimately
determining the impact that the local
geology and seismicity will have on the
final tank and foundation design. Properly
done, this detailed investigation enables
the contractors bidding on the storage
tanks to answer the following necessary
questions:
n
What is the expected uniform and
differential settlement?
n
What are the possible alternatives for
foundation and tank design?
n
Are there any obstacles or features of
the site that would impact the design
or determine construction methods?
n
What is the site’s seismic classification,
the corresponding liquefaction
potential, and most efficient tank
geometry?
Geotechnical
investigation
components
The information required to answer these
questions is derived from the three
components of a geotechnical
investigation:
n
The soil data report.
n
The interpretative soil report.
n
The site specific seismicity study.
Combined, these three components
create the geotechnical investigation.
Because each section provides unique
information, a cost effective and reliable
