COMPACTING
FILL MATERIAL CAUSES
COLUMN AND SLAB FAILURE |
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JOB
SITE: The photograph left shows exterior of the job site. The
front structure is used for office space. The warehouse area behind the office also
contained office space configured on two levels and supported by pipe columns off of
concrete footings. |
THE PROBLEM:
A leak in a drainage line under the slab caused localized failure of the
slab in the warehouse and a column footing that supported an office above the warehouse.
Soil tests revealed that the structure was constructed on uncompacted fill material
containing organics and debris. Settlement occurred at the column when the moisture caused
soil consolidation of nearly 5 inches!
THE SOLUTION:
The engineers proposed to install two Atlas
Modified Plate Piers on opposite sides of the settled pipe column. The pipe
column was mounted on a cylindrical concrete column cast upon a large rectangular
reinforced concrete footing. The engineers decided not to disturb or attempt to raise the
footing. The challenge was attach the Plate Piers to the round column and to drive the
piers through holes in the concrete footing.
First, a section of channel steel was welded to the round column so that
there would be flat surfaces to attach the framework that would hold the Atlas Modified Plate Piers. (See sketch on following
page.) The Pier Pipe would penetrate the existing footing via holes cored through the
concrete. The piers were each tested to loads exceeding 26,500 pounds. Then both of Atlas Modified Plate Piers lifted the column 4-1/2
inches with a force of 9,800 pounds on each. New mounting brackets were attached to the
column flange and secured to the existing concrete footing column. The 4-1/2 inch void was
filled with grout.
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| Engineered By:
General Contractor:
Ave. Driving Load:
Ave. Working Load:
Ultimate Capacity: |
Structural
Systems
Design, Inc.Ayars &
Ayars, Inc.
Omaha, Nebraska
27,350 pounds
9,785 pounds
90,000 pounds |
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| Installed
by:
Number of Piers:
Part Number:
Average Depth:
Factor of Safety:
Factor of Safety: |
Great
Planes Surfacing, Inc.
Omaha, Nebraska2
AP-PP(PA)-3500M
30 feet
2.8 : 1 (Working to Driving)
9.2 : 1 (Working to Ultimate) |
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The sketch above shows a plan view of the pier placement. Steel
channel was welded to the pipe column. The Atlas Piers
were then mounted on structural rectangular tubing spaced away from the steel column so
that the Plate Pier would clear the concrete cylinder below the column. The Plate Piers
were installed and tested to an average force of 27,350 pounds. Then a lifting force was
applied to both piers and the column was raised to the desired elevation. |
| The
photograph above shows a welder attaching the steel channel to the round pipe
column. The structure supporting the second floor office space is visible above the
workers. 
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The
photograph above shows a welder installing the structural steel tubing that was
used to extend the Atlas Modified Plate Piers
beyond the concrete column. The Atlas Piers
were driven to a solid bearing strata approximately 30 feet below the grade level. After
reaching solid bearing material 30 feet below the surface, each pier was load tested to
over 26,500 pounds.
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|
| The
photo above shows the technician installing the Atlas
Pier using quiet and vibration free hydraulic equipment. Above right is a view of the Atlas
Modified Plate Pier after the Pier Pipe had been driven to a verified bearing
stratum. 25 ton hydraulic rams are positioned over the Top Pier Platform of each Atlas Pier. Then the column is lifted by applying
equal pressure to each Pier.
SUCCESS!
The photo right shows
how the column was restored to the proper elevation some 4-1/2 inches above the concrete.
Steel legs were later welded to the base of the column to secure the column to the
concrete. The void was filled with grout.
THE SOLUTION:
Atlas Piers!
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