OWNER:
Alabama State Docks
P.O. Box 1588
Mobile, Alabama 36633-1588
PROJECT
ENGINEER:
David Volkert & Associates, Inc.
3809 Moffett Road
Mobile, Alabama 36670
DESIGN/CONSTRUCT
CONTRACTOR:
Synergy Earth Systems, Inc.
In
1999, the Owner agreed to construct a barge dock for IPSCO Inc.,
a Canadian steel company. The Owner elected to construct the facility
at a site located on the western bank of the Mobile River, adjacent
to IPSCO's new Mobile Steelworks Mill in Axis, Alabama. Completion
of the structure for the unloading facility and for an adjacent
access bridge required construction of an earthen platform and a
bridge approach embankment. The geotechnical investigation performed
at the project site indicated that approximately 5 feet of recently
placed fill was underlain by about 30 feet of soft, compressible
soil. The presence of this compressible soil made the design and
construction of the embankment and bridge approach challenging,
with settlement and slope stability being two of the key design
considerations.
Synergy
Earth Systems, Inc. (SES) was retained directly by the Owner to
design and construct the earth platform and associated bridge approach
embankment. SES used a matrix design approach to determine which
combination of soil improvement technologies would address the key
design considerations and result in the most efficient and cost
effective design. Several technologies, including horizontal reinforcing
geogrids, vertical wick drains, staged construction and surcharging
were considered in the matrix. Ultimately, all of the technologies
were utilized. A staged construction schedule was utilized to allow
the compressible foundation soils to consolidate and gain strength
under the newly placed embankment load. A surcharge was also applied
in order to pre-consolidate the foundation soils and minimize post-construction
settlement.
Construction
of the docking facility was performed in two phases. Phase I consisted
of construction of the bridge approach embankment. Phase II consisted
of construction of the earth platform and sheetpile bulkhead. Phase
I of the construction was successfully completed by SES over a one-month
period in October-November, 1999. Over 8,000 square yards of geogrid
and 130,000 linear feet of wick drains were installed in the bridge
approach embankment. Phase II of the construction was begun in June
2000. For this phase of work, over 18,000 square yards of geogrid
and 93,000 linear feet of wick drains were installed. As part of
the Phase II work, SES designed and constructed approximately 2,800
square feet of wrapped face soil reinforced wall behind the sheetpile
bulkhead. This wrapped face retaining wall reduced pressure on the
bulkhead and allowed a smaller pile section to be used. The construction
is complete and the facility is ready for use.
