PROJECT SUMMARY:
To allow for the final leg of the Cross-County Metrolink
extension into Shrewsbury, engineers needed a wall system to
support the light rail as it descended from its crossing of Interstate 44
into the Shrewsbury Station location. As with all walls
on the Metrolink project, these had to meet very stringent
specifications called for by Metrolink.
PROJECT SOLUTION:
A 90,000 square foot wall system was designed by Ed Austin of
Aspen Consultants and Leo Turick of Brucker Engineering according to Metrolink and KCI design
specifications. These stipulations required specially
manufactured 100 pound Rockwood blocks for the finished
construction. In all, 10,000 truckloads of rock backfill
(or 250,000 tons) were used behind this wall system at
Shrewsbury Station and along the alignment. The undertaking lasted almost two
years and due to time and other design considerations
grew in value to almost $3.7 million.
SPECIAL CONSIDERATIONS:
The project provided a significant construction challenge in
that a significant amount of settlement at Shrewsbury
Station was expected by
engineers on this project (around 22"). For this reason
geotechnology engineers developed a four phase building process
which would extend the project length considerably and require
the construction of a temporary retaining wall. During
the process this temporary wall with attached reinforcing grid
was built in phases of 8' heights. Rock backfill was
installed in 8' lifts and the temporary wall was constructed
with settlement plate sensors -- or a way for engineers to
check how much the wall was settling over time. After a
given number of weeks if the wall showed no (or little) signs
of settling, the next phase was allowed to proceed.
Once the settlement phase of the operation was completed, the
permanent wall was then built in place in front of the
temporary wall. Nothing of this type or magnitude had
ever before been attempted in St. Louis.
PROJECT RECORD:
The completed
connection between the Ideal wall and a section of
elevated Metro track at Big Bend and Oxford.
Ideal workers
prepared a base course of the wall.
One of thousands of
truckloads of backfill arrives at the site.
Compacted backfill
behind the wall al approximately half its final height.
This curved section
of wall gives a good view of the back fill behind each
course of block.
The wall rises course
by course.
A section of the wall
approximately half completed.
A shot of the wall
near its final height. The shopping plaza at Oxford
and Big Bend can be seen of to the left.
A completed section
where the elevated Metro tracks meet the wall.
