July/August 2024 - 118

Forensic Case Study Results
While the attempt to construct an MSE
wall in the Sydney airport expansion is
a professional challenge, the costsavings
compared with an alternative
wall system was not very significant. In
fact, the design-build winning project
was about A$20 million (about $13
million) cheaper than the alternative.
Reported overall cost of the project,
where the MSE was only one component,
was about A$200 million. The
risk associated with such utilization
should be limited to less significant
applications. Only when there is an
abundant experience, could a new and
innova t ive appl i -
cation be used in a
scale such as the
airport.
This case ended up
two-thirds of it details the geotechnical
aspects, considering the evidence provided
by all experts. The judge's grasp of
the technical issues is commendable;
the full judgment can be downloaded at:
https://spaces.hightail.com/receive/
rjNDSBeRic. It provides an excellent
explanation of the issues. A personal
lesson from the judgment is the critical
importance for an expert not to serve as
an advocate as it may lead the judge to
declare one evidence as not credible. It
is noted that the case was appealed by
the plaintiff. In October 2008, the three
judges in the Court of Appeals dismissed
the appeal.
Compaction behind the facing of
any MSE wall is important. It creates
an integrated system of facingreinforcement-soil.
It also prevents
in-service down movement of backfill
against the facing resulting in
parasitic load on the reinforcement at
the connection.
Drainage is essential to successful
performance of any MSE wall. Water
decreases the shear strength of soil
resulting in excessive deformations
and possibly in collapse.
Quality control during construction
The full judgment can be downloaded at:
in New South Wales
Supreme Court. The author had the
privilege to appear as an expert in this
non-jury trial in November 2005. The
judge had warned the author that his
task is to advise on the forensic finding,
not to advocate for the paying party.
Being honest and transparent was
essential. The author has spent two and
a half days on the witness stand,
subjected to professional cross examination
by an educated barrister. The
expert for the plaintiff spent more 10
days on the witness stand.
Judgment was rendered in 2006 and
it is more than 300 pages long. Around
Conclusion
The discussed two cases which, when
combined with experience with other
failed MSE walls, lead to several general
lessons.
Compaction is extremely important.
It increases the strength of soil, reduces
settlement and provides redundancy as
designers tend to underestimate the
beneficial impacts of compaction. For
example, typically designers will use
shear strength that is much smaller than
the real value thus producing conservative
structure. This redundancy is, in
essence, an undeclared factor of safety.
is also extremely important. It ensures
that the design assumptions are met
and that the performance
meets the design
expectations.
https://spaces.hightail.com/receive/rjNDSBeRic.
Communication
among al l part ies
involved in design
and construction must be facilitated so
as to avoid errors and omissions and to
ensure that design assumptions are
met in actual construction.
Dov Leshchinsky, Ph.D., is an emeritus
professor, retired from the University of
Delaware after 32 years of service where he
conducted research on slope stability, soil
reinforcing, geosynthetics and dredged
materials. Prior to joining the Delaware
faculty, he worked as a geotechnical engineer
with the Association of American Railroads
in Chicago.
118 * DEEP FOUNDATIONS * JULY/AUG 2024
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