Multi-Family Residences Case Study

Minimizing Risk With Ground Improvement

The Multi-Family Residences Project is in our nation’s capital, Washington, D.C. The project is a proposed multi-family residence structure that was struggling with poor soil conditions. CNC Foundations has spent the past 30 years supplying ground improvement solutions for situations like this.

Why Was CNC Foundations Needed?

Project: Multi-Family Residences

Location: Washington, D.C.

Product Type: Aggregate Piers/Vibratory Stone Columns

The existing fill on the jobsite consisted of loose silt, sand, clay, and gravel. It could not successfully sustain the weight of the proposed structure. Without intervention, it ran the risk of significant future settlement.

Settlement, to some degree, is a natural part of a building’s life cycle within the first few years following construction. Excessive settling can become an issue that weakens the foundation, causing cracks, and impacting building services like plumbing.

One of the leading causes of significant settlement is a weak bearing soil like the conditions that were present for the Multi-Family Residences Project. Issues with settlement can be resolved later in the life of a building, but it is always best to be proactive about these issues.

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What Did We Install?

To help prevent future ground settlement, CNC Foundations installed aggregate piers/vibratory stone columns (VSC) through 20 feet of the fill. The VSCs were extended through the existing soil into the more dense sand and gravel layer.

Vibratory stone columns are compacted columns of aggregate that are installed through the current soil. The goal is to improve the geotechnical properties of the soil matrix. The stone columns are made up of a series of vertical lifts of compacted aggregate from a predetermined design depth up to the ground surface.

This particular installation provided 5,000 pounds per square foot (psf) bearing capacity and limited total settlements to less than 1 inch. Also, to help minimize the number of vibrations from the VSC installation process, we also pre-drilled along the existing neighboring theatre building.

What Was the Result of the Project?

Resident Project now has firmer and more stable ground to stand on for the future. Through our many years of service, we have earned a reputation for more than just success. We have become known for helping clients win bids, lower costs, and meet the demands of challenging projects.

Our safety record is another point of pride for us. We always make safety our first priority. All of our personnel are trained and certified for HAZMAT (hazardous materials), Occupational Safety and Health Administration (OSHA), and Mine Safety and Health Administration (MSHA). We’ve become the popular choice for geotechnical design/build and ground improvement thanks to our extensive library of services and capabilities. To learn more about the work CNC Foundations does and how we can assist with your construction project, contact us today.

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