Challenge

November 2012 - Building 4602 within the Skaff Apartments complex was constructed in 1987 of wood framing and brick veneer over poured concrete foundation walls and footings. The two-story structure has a partially buried daylight basement level and approximate plan dimensions of 57 feet by 170 feet. Signs of distress on both the interior and exterior of the building generally indicated settlement of the 170-foot long south (rear) wall of the building. Drywall cracks were observed in the corners of rooms and above doors and windows, some doors and windows were misaligned and did not operate properly, and the concrete floor slab along the south wall of the building sloped downward to the south. Outside the building, the expansion joint within the brick veneer on the west wall, approximately three feet north from the southwest corner of the building, indicated both vertical and horizontal movement. Soil testing was not performed at the site; however, it is fairly common to encounter plastic clay soils near the surface within the Red River alluvial plane. Based upon the age of the structure and the fact that the movement was observed within the past two years amid drought-like conditions, it was concluded that the foundation settlement was likely due to drying and shrinking of the foundation soils. The owner was searching for a cost-effective repair solution that would stabilize and possibly lift the structure back toward its original position, while also minimizing disturbance to the property.

Solution

Thirty-two (32) Model 288 (2.875-inch O.D. by 0.165-inch wall) hydraulically driven push piers were proposed at a six-foot maximum spacing to underpin the south wall and the southeast and southwest corners of the building. A continuous trench excavation was made outside the building to expose the footing. The footing was notched back to the face of the foundation wall at each pier location to install retrofit foundation bracket assemblies. The push piers were advanced to depths of 70 to 88 feet below bottom of footing elevation to bear on competent material. The piers were driven to hydraulic fluid pressures averaging 4,000 psi, corresponding to 38.5 kips of drive force. Hydraulic cylinders were used to stabilize and then uniformly lift the wall approximately ¾-inch back toward its original elevation. The excavation, footing preparation, pier installation and site clean-up was completed in five days.

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Project Summary

Certified Pier Installer: Innovative Foundation Supportworks®

Products Installed: (32) Foundation Supportworks® PP288 Push Piers, Installed to Depths from 70 to 88 feet Below Bottom of Footing, Design Working Load of 25 kips