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GEOFOAM OUTWEIGHS OTHER OPTIONS
BRANDYWINE TOWN CENTER, WILMINGTON, DELAWARE
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An opportunity arose to obtain Target "Greatland" as a tenant
for a building that was under construction. To attract this retailer,
the partially constructed building had to be enlarged. The only space
available on which to expand the existing building was an adjacent
parking lot.
The proposed expansion onto the adjacent parking area presented many
challenges, the most significant of which was a grade differential
of over 10 feet between the existing building's floor elevation and
the ground surface behind an adjacent recently constructed mechanically
stabilized earth (MSE) retaining wall. Additionally, the proposed
design would have to consider the constructed portions of the building,
the retailer's requirement for more space and high rack storage loads,
schedule requirements, and budget constraints. Duffield Associates
was consulted to develop an alternative solution.
Conventional earth fill was not feasible without rebuilding the
MSE retaining wall, which had not been designed for such a large
grade differential. Reconstruction of the existing wall could not
be completed within the required schedule. Supporting the entire
building addition on deep foundations was considered too costly.
To design an innovative and cost effective solution, Duffield Associates
used state-of-the-art computer-assisted modeling to evaluate the
interaction between the existing wall and the proposed building
expansion. Our solution allowed the heavy floor loads from the proposed
building addition to bear directly on underlying subgrade soils
within the existing retaining wall's influence zone. This was made
possible by using a fill material made of Geofoam; a lightweight
expanded polystyrene foam. Because Geofoam weighs less than 1½
lbs. per cu ft, it could be placed behind the existing retaining
wall without imposing additional forces. In order to compensate
for the new heavy floor loads, some of the existing soil backfill
beneath the building addition was also removed and replaced with
Geofoam. Unlike time-consuming and weather-sensitive conventional
earth fill operations, this unique approach required only 3 days
for installation and allowed the project to proceed on schedule.
The combination of the MSE wall with the Geofoam represents a new
innovation.
Not only is Geofoam cost-efficient, but it is environmentally friendly.
Geofoam, which does not contain chemicals that harm the environment,
is highly stable and will not decompose or produce undesirable gases
or leachates. Another environmental advantage of Geofoam is that
it is recyclable and it can be made of recycled materials.
Duffield Associates satisfied the client's expectations, saved
construction costs, facilitated flexibility in development plans,
and, despite the changes enabled the project to be completed on
time. Our innovative fill solution was awarded the 1999 Consulting
Engineers Council of Delaware Engineering Excellence Honors Award.
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