Newpoint V Case Study

PROJECT: Newpoint V-Lawrenceville, GA

CONTRACTOR: The Conlan Company

SUBCONTRACTOR: Cantsink of Atlanta, LLC

ENGINEER:

Civil– Jordan, Jones and Goulding, Inc.   Norcross, GA

Structural– Browder-LeGuizamon and Associates, Inc.  Atlanta, GA

Geotechnical– United Consulting  Norcross, GA

SITUATION: This project involved the development of a site for a single story office warehouse building, approximately 268,000 sq ft.  Preliminary soil testing revealed areas of the buildings foundation to bear over unsuitable or questionable soils.  This was determined through 20 soil borings to terminated depths of anywhere from 15 to 25 feet.  The soil conditions varied from sand-some silt, to silts-sand, and organics.  The problematic soils were identified and the Geotechnical engineer suggested those areas be supported on a deep foundation system consisting of either helical piers or drilled shafts bearing in competent residual soils. To assess a more accurate cost for considering helical piles on this project, Cantsink of Atlanta installed seven (7) test piles.  The results concluded helical pile depths to range from 17 to 42 feet.  While the depth range varied, there was a consistent pattern of the pile depths corresponding to the soil borings performed.  The Structural Engineer’s design reflected a total pile count of 185 locations.  The designed service loads were 30 Kips compression and 12 Kips tension.  While drilled shaft piers were strongly being considered, the likelihood of encountering groundwater would require the use of temporary casings.

SCOPE OF WORK: The site had been prepared prior to installation of the test piles.  Following receipt of the budgetary cost for helical piles, Cantsink of Atlanta was hired to proceed with installing the required helical piles.  A 5,500 ft-lb hydraulic drive head mounted on a Bobcat S250 skid steer loader was used to install the helical piles for this job.  The 185 piles were installed in five (5) days with the footage exceeding 5,200 lf.  No disturbance of the site occurred.  The pile depths were consistent with the test piles performed resulting in a margin of error of less than 1%.

Piling System: The piling system specified was a 2.5 inch schedule 40 steel shaft (3” nominal) with a single 14” diameter helix.  The material included 10.5’ lead sections, along with 5’ 7’ and 10.5’ extensions.  The piles were manufactured by Cantsink Manufacturing, and installed by Cantsink of Atlanta, LLC.  Pipe caps for each pile included a 8” x 8” x 3/8” plate sleeved into the top of pile and through bolted for uplift restraint.  Working loads of 30 Kips per pile were achieved as measured through torque gauges during installation.  All piles were monitored by United Consulting and certified.

RESULTS: Pile depths ranged from 15 feet to 47 feet with a consistent pattern for specific areas of the building.  Final pressure reading of torque for the piles ranged from 2900 to 3000 psi for the drive head.  The applicable kt factor for the soil conditions yielded the desired service loads per design.  Installation was completed ahead of schedule, with no damage to the site, excavated footings or form work.  An article about Cantsink Manufacturing was featured in the April 16, 2007 edition of Dixie Contractor magazine, and included the site of this project.

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