This type of system is common in the DC Metro area. The foundation walls of below-ground parking structures may be constructed as one-faced reinforced concrete walls. Design of the wall drainage system is a big factor in the design.
Retaining Structures
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This type of system is less commonly used than a tieback system because the inside of the excavation is left open for construction activities with tieback systems.
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A sheet pile system was used near the Cheasapeke Bay to excavate a trench in sand 20 feet below groundwater. In this photo, the cofferdam is being dewatered as the excavation proceeds. The tunnel was then constructed and backfilled with flowable fill. PCC provided design services for the general contractor on this project.
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When a sheet pile cofferdam system is not rigid enough, a slurry wall such as this one may be used to provide both temporary and permanent support of the excavation.
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PCC designed and monitored construction of this 34-ft. tall geogrid-reinforced Keystone wall.
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The sides of this quarry are being stabilized by constructing soil nailed walls with artisticly carved and colored shotcrete facing. The total height will be up to 75 feet with individual walls of 10 to 40 feet in height. PCC is working for the design-build wall contractor on this site.
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The wood facing on this wall was pulling apart. PCC provided geotechnical exploration and consulting to the structural engineer. We have worked on several other types of walls that are not common to the Metro area.
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Timber retaining walls may be less expensive to construct but the usefull life depends on the design, construction and subsurface conditions. Walls like this one need to be replaced.
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This building is supported on top of a wall that is acting as a retaining structure. The wall is made with steel cantiver piles and cast-in-place concrete facing. PCC, working for the developer, assisted the contractor in design and provided construction monitoring.
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Reinforced concrete and masonry retaining walls generally have good longevity. The reinforcing can get complex and expensive even in a relatively small height wall. This is the foundation of a 2-tiered closely spaced concrete wall that PCC designed and monitored.
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Basement walls need to be designed to resist earth and sometimes water pressure. PCC has been involved in the repair or replacement of below grade walls on many projects. In this example the wall has been completely removed and will be replaced. For more information, see Forensics.