ribs of T-wall precast sections in how the sheet pile wall concept
works. Basically, the perpendicular sheets serve as vertically planar
tiebacks, i.e., fins, providing resistance to lateral loading acting on
the wall through the following mechanisms:
a. soil/steel interaction, i.e., friction, and
b. the dead weight of the fins including soil contained within
them to provide additional restoring moment.
Critical to our assessment of the viability of the sheet pile wall
system was that sheet piles indeed could be driven through existing
embankment without too much difficulty, which available test
boring data did confirm.
The sheeting was founded at the same depth and approximately
the same horizontal extent as the as-designed MSE wall so as to
effect similar global stability results to the as-designed wall structure.
Additionally, temporary shoring was not required to build this
sheet pile wall alternative – a significant result of which was that
instead of a two-stage temporary shoring installation and then
wall construction as would be required for either an MSE wall or
T-wall, only one stage – the actual construction of the wall – was
necessary to build this sheet pile wall. This resulted in the realization
of significant time savings in addition to cost savings.
Future value to the engineering profession
and the highway industry
By virtue of the cost savings, this value engineering retaining wall
alternative has provided the contractor and owner this unique
retaining wall alternative, which to our understanding has never
been constructed along a highway requiring widening before. The
project’s success has demonstrated that a less expensive solution
involving this sheet pile wall system has potential for similar-type
highway widening projects in the future. And given that it took only
six months to construct this permanent sheet pile wall system – as
compared to an 11-month estimate for the as-designed MSE wall/
permitted T-wall – one can only imagine the real cost savings that
this sheet pile wall alternative would provide if this work item were
on the critical path.
PROJECT SPOTLIGHT
Key Project
Statistics
• Length of Wall: 1,573 feet
• Max. Height of Wall: 21 feet exposed overtop
existing 1.5:1 embankment slope
• PZC 26 Wall Face Sheets and PZC 13 Fin
Sheets: 2,000 tons of steel
• Type C Flowable Backfill (300 psi): 5,200 cy
• No. 57 Coarse Aggregate: 1,100 tons
So, with this successful installation of our permanent sheet pile
wall system of rather pleasant aesthetics (Figures 4 and 5), our
hope is that this wall system will be used for the future widening
of other roadways on embankment, thereby allowing for this new
technology that incorporates longstanding construction material,
i.e., steel sheet piles, typically only used in temporary support of
excavation applications, to be used in a heretofore non-obvious,
novel and useful fashion as word of this first such application
spreads with further exposure. As long as sheet piles can be driven
without too much difficulty, it is our belief that this sheet pile wall
system to provide for highway widening in embankment conditions
should be considered for any highway project where adjacent,
active traffic must be considered. t
Michael Sydlik, PE, M.ASCE is president of Earth, Inc. in Pittsburgh,
Pa., a specialty geotechnical engineering company firm he started in
1983. Richard Morales, P.E., M.ASCE is director of engineering at L.B.
Foster Company, a position he has held for 11 years.
Photos: Earth, Inc.
Figure 4: Completed wall showing both widened roadway and steep
existing embankment slope below wall
Figure 5: Downslope side of completed wall
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