Atlas Piers of Atlanta, Inc. P.O. Box 3313 Alpharetta, GA 30023 Phone: 770-740-0400 Fax: 770-740-1513

FAILING RETAINING WALL THREATENS APARTMENT FOUNDATION STABILITY

Roswell, GA

Installed by: Atlas Piers of Atlanta, Alpharetta, GA

THE PROBLEM

The photograph shows the sagging and misaligned retaining wall. A failed attempt to salvage the wall can be seen along the lower portion of the wall.

Description of Site:

This apartment complex is situated on a sloping area that required “cut and fill” of the natural contours to prepare building sites. The soil was a dense silty clay that experienced shrink and swell cycles.

 

Description of Structure:

The existing retaining wall was constructed of used railroad ties with little or no engineering thought in the construction of the wall nor the backfill against the wall. The wall varied in height up to 15 feet. The average height was 13 feet from grade.

 

Description of Findings:

The engineers recommended that a new wooden retaining wall be constructed approximately two feet in front of the existing wall. The new wall was constructed of all new materials and restrained by two rows of ATLAS-Helical Tieback Anchors spaced 6-1/2 feet center to center along the wall.

The sketch shows details of the project including the Atlas-Helical Tieback Anchor placement and attachment.

The poor condition of the existing wall is evident in the photo to the left. Visible below the man are the galvanized transition couplings and threaded bars that were attached to the lower row of anchors. RAPID INSTALLATION! The ATLAS-Helical Tieback Anchors were installed using a portable 4,500 ft-lb hydraulic gear motor. Small access holes were made in the existing retaining wall at approximately 4-1/2 feet from the lower grade level. The lower row of anchors were installed to an average length of 14 feet and to a target terminal torque of 2,200 ft-lbs. The upper row of anchors were installed in a similar manner, but were located approximately 3-1/2 feet from the upper grade level. The design load for the upper row of tieback anchors was 15,000 pounds and the lower row was designed for 17,000 pounds.

The photograph to the right shows two openings that were cut into the existing wall, the hydraulic gear motor and a starter section that has been partially installed.

Each ATLAS-Helical Tieback Anchor was composed of a 2-7/8 outside diameter tubular shaft with three helical plates welded to the shaft. The first plate was 6 inches diameter with a spiral “sea shell” shape. The next two helical plates had a diameter of 8 inches. The spacing between plates was specified at four times the previous plate diameter.

The poor condition of the existing wall is evident in the photo above. Visible below the man are the galvanized transition couplings and threaded bars that were attached to the lower row of anchors.

The photograph above shows the workers installing one of the upper tieback anchors. The lower row of anchors has already been installed. The continuous thread bars are visible extending from the new timber wall.

The photographs below show the details of the tieback anchor installation and wall construction.

Above are views of the wall at 50 percent complete.

The workers are installing the upper row of anchors. Note the continuous thread bars protruding through the new wall. These are connected to the lower row of anchors.

The project was quickly completed with very little disruption for the occupants of the apartments. The quiet, vibration free hydraulic motor was able to rapidly install the 58 anchors. The new construction was designed for a useful life of ten years.

Atlas Piers of Atlanta, Inc. For more information please contact us at info@atlaspiers.com Office: 770-740-0400 Fax: 770 740 1513