Project:
Sector – Large Residential Property, District Rehabilitation
Location – Elmwood, IL
Application(s) – Earth Retention, Helical Underpinning, Permeation Grouting, Secant Wall, and Helical Tie-Backs

Project Description:
In June of 2010, a tornado struck the city of Elmwood, Illinois. The tornado caused damage to several buildings downtown, including one with damage so extensive it had to be condemned and torn down.

The building was three stories and rested on shallow foundations. The owner of the building wanted to rebuild this key structure in the downtown area, complete with a clock tower and add a basement intended for an artifact museum. This was problematic due to the surrounding buildings and their footing elevations requiring earth retention systems at three key areas around the building site.

Project Requirements & Challenges:
Each area of the building site had its own unique challenges. On the South wall of the site was a building resting on a thickened slab. The West wall had an existing building resting on a stem wall that extended approximately 7 feet below grade. Both buildings were approximately 75 years old. Highway 78 and multiple utilities ran along the North side of the building. Helitech was hired to design an earth retention system that could be tailored to each unique challenge.

Solution:
South Wall:
The south side of the building site butted up against an existing building resting on a thickened slab. The top 6 feet of soil on the job site was sand. Helitech first underpinned the existing slab using helical piers. We then used permeation grouting to bond the sand together so that the face of the cut would not collapse. Once we were past the initial 6 feet of sand, a soil nail wall was installed to retain the soils down to 15 feet.

Time of completion: 7.5 days

West Wall:
The West side of the building site butted up against an existing building with a stem wall that extended approximately 7 feet below grade. For this section, it was decided to install a secant wall with tie-backs to retain the soil. The grade beam was poured on top of the secant wall acting as a waler.

Time of completion: 6 days

North Wall:
The North side of the building site runs along Highway 78. It was decided that a secant wall, without tie-backs, was the best solution due to existing utilities and property rights.

Time of completion: 3 days

Results:
No movement was recorded in the two (2) existing 75 year old buildings. The project was completed safely, on time, and on budget.

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