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 Back to Projects
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Project:
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Bushwick Shaft 20B (1992)
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Location:
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New York, New York
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Client:
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Schiavone Construction Company
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Description:
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Construction of a 46-foot diameter, 300-foot deep shaft was attempted using the slurry diaphragm
wall method for earth support and groundwater control. During the initial excavation, three breeches
in the joints between slurry wall panels created significant inflows of groundwater and loose sandy
materials. These inflows manifested themselves in the form of settlements of several inches of the
surrounding streets and minor deformation of several structures in the immediate vicinity.
Layne Christensen installed and maintained a ground freezing system around the perimeter of the entire
shaft, extending approximately 300 feet into bedrock. Freeze pipe installation was accomplished
utilizing Layne's Dual Wall Reverse Rotary System, which can decrease installation times of
refrigeration pipes by one half. This drilling method was extremely successful in soils that had been
grossly disturbed by the slurry wall failure and resulting blow-ins.
Due to the complexity of the surrounding area which included several buried utilities and an adjacent
subway tunnel, any problems with the frozen earth wall could be devastating. An extremely rigid
quality assurance program was implemented which included measuring of pipe deviations at 2-foot intervals,
precise flow rate and volume measurements and electronic ground temperature monitoring and over 100
thermocouples to measure and ensure balance of the coolant flow.
Due to the large diameter and depths of this excavation, considerable deformations were anticipated.
Finite element modeling of these creep deformations were compared with field results to ensure that the
actual creep deformation did not interfere with the placement of concrete form.
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