CNC Foundations, Inc.

Scope Of Work

Product Type: Vibratory Stone Columns (VSCs) & Load Testing Process

Wind energy is quickly becoming an essential part of the modern economy. It is a renewable form of energy that creates almost no waste. This technology is stimulating job growth in clean energy and aiding economic development around the country. Even without the environmental benefits, wind energy is a valuable source of power. This growth in renewable energy also means more work for specialty contractors like CNC Foundations.

The foundation support systems for wind turbines are unique. The wind turbines are mounted to towers and the height of these towers makes them susceptible to the force of the same winds powering the turbines. The towers will tip in the wind and the foundation must resist this force to stop the tower from rocking. The foundation for these towers must also stand up to elements like earthquakes and other natural factors.

What Did We Install?

We work with many structures that have to deal with substantial heights, but wind turbine foundations have strict differential settlement tolerances across the footing width. The large overturning moments caused by the wind can lead to differential settlement problems in soft soil and they require additional foundation support.

That is where our services with vibratory stone columns make their impact. Our certified rig operators installed VSCs through soft clay and loose sand up to 18 feet below the existing grade at 13 turbine locations. The purpose of the VSCs was to control total settlement of the wind turbines and minimize differential settlements expected from the large overturning movements so the turbines can perform as planned.

As a load testing process, we performed a full-scale modulus test at every turbine location. Due to the depth of wind turbine foundations, we developed a specific load testing process to measure the modulus of the VSC within the zone of soil below the final turbine foundation bearing elevation. This custom procedure consists of installing a sacrificial test outside the turbine footprint and a concrete-filled sonotube shaft to the bottom of foundation elevation. This enables the VSCs to be tested at the final elevation to provide the best representation of their long-term performance.

What Was the Result of the Project?

CNC Foundations developed a detailed testing Quality Control plan to ensure the full-scale modulus test at each turbine is installed and performed consistently. This sequence not only qualifies our design, but is performed to keep the project on schedule and includes the Closeout Document Process. As part of CNC Foundations’ quality control plan is the reassurance from our closeout document process to provide the client with the VSC logs, test results, and as-built drawings within 48 hours of completing each turbine.

The owners and operators of the wind farm now have the peace of mind that the foundations on all of their towers are secure and the closeout documents have been reviewed and approved by CNC Foundations’ engineering. Peace of mind and security like that is part of the reason so many customers rely on CNC Foundations. We have the expertise to deliver the work you need and the experience to provide the compliance your business requires. Count on CNC Foundations for unmatched support and superior workmanship. Contact us today to learn more about specialty services.