July/August 2024 - 114

* A conclusion identifying the most
likely reason(s) leading to the poor
outcome.
It is noted that a forensic study is,
essentially, reverse-engineering. That
is, the end-result is known, and one
then looks for plausible reasons for this
outcome. This article follows the
process and identifies the primary
reasons for failures following extensive
analysis and examination in field and
lab data. Universal lessons learned are:
* Ignorance is the mother of all sins,
i .e. , mistakes due to l imi ted
perspective and understanding can
lead to major failures.
*
Little savings in cost may lead to
very expensive remediations.
* Lack of redundancy could be overly
optimistic, potentially leading to
failure.
Case Study I - Georgia
Construction of a geotextile reinforced
wall with wire basket facing was
completed in late 2001. In spring 2003,
performance problems were apparent
including a singular location where
water drained from the wall zone
channeled to a detention pond. The
wall's maximum height was about 53 ft
(16 m); the nominal height of the wire
baskets was 18 in (457 mm). Alternating
primary and intermediate
woven geotextile layers were placed
every 18 in (457 mm), corresponding to
the wire facing. The backfill in the front
12 in (305 mm) was clean gravel and the
reinforced backfill was random,
supposedly with no more than 35%
passing sieve #200, compacted to 95%
according to the Standard Proctor
method. Following rainfall, there was
significant settlement resulting in
cracks of the building on top. This was
The geotextile reinforcement,
still embedded in the
soil, became obsolete as
performance was hinging
only on the anchors.
Anchors supporting a wall in Georgia (Courtesy of Rick Valentine)
Risers collecting surface water, connected by
horizontal 8 in (203 mm) pipes
accompanied by soil depression around
surface water collectors - the entry
areas to risers. The owner filled these
depressions with concrete to level the
surface with the existing asphalt
driveway. In spring 2003, the building
on top was closed and remediation
conducted. Repair work was massive,
using anchors, basically " solidifying "
the reinforced soil and costing several
times the original cost of the wall. The
geotextile reinforcement, still embedded
in the soil, became obsolete as
performance was hinging only on the
anchors. The case was settled out of
court in summer 2004.
Forensic Study Observations
and Conclusions
A number of observations were made
during the forensic study. First, the
contractor had to add 10 in (254 mm) of
fill on top of the upper layer to reach
the final grade. The foundation soil
was firm (rock), and foundation
settlement could not explain the need
to add backfill. Compression of the
backfill under its own weight due to
poor compaction provides a sound
explanation.
Surveying of the face conducted
before closing the area for repairs
showed that all the wire baskets
compressed with the backfill behind
and were shorter than their nominal
height of 18 in (457 mm). Adding the
cumulat ive deformat ion of the
compressed wire baskets indicated
total compression (including the 10 in
114 * DEEP FOUNDATIONS * JULY/AUG 2024
July/August 2024

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