THE PROBLEM:
The building began showing signs of structural distress soon after construction began. The basement floor slab showed signs of significant movement. A fracture in the basement floor was noted approximately 4 to 6 feet from the perimeter wall. The floor sloped downward from the crack to the perimeter walls. Most of the initial movements occurred on the exterior walls of two sides of the building, but the engineers predicted the entire structure was at risk.

SITE CONDITIONS:
General grades across the site sloped to the rear by nearly five feet. Borings were made on the site. The borings revealed sandy or silty clay fill to a depth of 11 feet. Under this was a 20 foot layer of peat and organic clayey silt! Beneath the organic soils were silty sands, sandy silt, sand and clayey silt. Much of the peat was very loose. Standard Penetration Tests of the peat were impossible as the weight of hammer (WOH) pushed the sampler over one foot. The organic clayey silt was very soft with unconfined compressive strengths of less than 500 psf. Groundwater was at depths of 13 feet.

THE PLAN:
The Engineer specified Atlas 2-Piece Resistance Piers to be installed on the perimeter. This layout would completely support the foundation to firm bearing, far below the problem soils. Atlas Resistance Slab Piers supported the interior column foundations.

The photographs above show the Atlas 2-Piece Resistance Piers installed along internal basement walls. Each pier was driven to a suitable bearing stratum below the poor soil. After reaching refusal, each pier was individually tested to a load greater than the force required to support the foundation. To restore the structure closely to the original elevation, 25 ton hydraulic rams were positioned on each Pier and the Piers were loaded uniformly.

This is a view of two Atlas 2-Piece Resistance Piers located on an external basement wall. Note the hydraulic rams and manifold assemblies used to distribute the hydraulic pressure equally to each pier.

THE INSTALLATION PROCESS:
The Atlas 2-Piece Resistance Piers were installed using quiet, vibration free hydraulic equipment. Each pier was driven to a suitable bearing stratum using portable equipment. The building structure was used as reaction to the driving force. Technicians carefully recorded the installation forces involved at regular intervals.

SUCCESS! The photograph left shows a detail of the lifting process. The hydraulic ram was installed between the Lifting Head and Atlas 2-Piece Resistance Pier. Once restored, the load was removed from the ram and transferred to shims and the two Pier Pins that are visible on either side near the base of the hydraulic ram. The Lifting Head and ram were then removed. The foundation restoration project was completed quickly and construction resumed on the house.   Atlas Piers THE Solution!

Atlas
Slab Piers!
The interior columns were supported and restored using Atlas Resistance Slab Piers. The Piers were easily and quickly installed through drilled holes in the concrete slab and footing.

The photograph at left shows lifting the floor and a column using four Atlas Resistance Slab Piers. Below each circular Lifting Plate was a 25 ton hydraulic cylinder. Once the desired elevation was achieved, nuts were tightened to transfer the load to the Pier. After load transfer, the rams and Lifting Plates were removed and the holes repaired.

Chance Civil Construction
1026-B South Powell Road
Independence, MO 64056
Office: (816) 796-6800
Fax: (816) 796-0919
Toll Free: (877) 285-2739
Email: info@atlassys.com