Foundation Support Finalized for Turbine Farm

See how CNC Foundations utilized vibratory stone columns to a new wind farm in central Texas.

The Problem

A client building a wind farm in central Texas needed a ground improvement system to support the structure. The soil conditions beneath the turbine elevations consists of soft clay, which could lead to long-term differential settlement issues without specialized foundation support. The client reached out to CNC Foundations because of our experience working on wind farm projects.

Our Solution

CNC Foundations was engaged early on in the project by the general contractor to evaluate ground improvement options for these foundation locations. Several ground improvement options were considered, and aggregate piers, also called vibratory stone columns or VSCs, were selected by our engineering team as the most effective solution to support these very large and heavy wind turbines.

We designed the aggregate piers/VSCs to limit total and differential settlement while increasing the allowable bearing capacity at each location.

The Results

CNC Foundations was able to keep an efficient schedule and sequence by utilizing its direct-push method of installation. Limited spoils generation prevent excess material handling, and it allowed the client to improve their construction schedule. As part of our exception QA/QC, a full-scale modulus test was performed at each turbine location to ensure the ground improvement system was installed as engineered to perform long-term settlement control as intended.

Quality Assurance and Control

CNC Foundations has created a comprehensive quality assurance and control process, which we implement for every project.

Each project is validated by an outside, third-party design firm. This process guarantees an independent peer review to ensure that the design will meet the project’s requirements.

The aggregate pier design submittal produced for every project includes the calculated pier elastic modulus (pier stiffness) and the top of pier stresses for each footing type on the job site. CNC Foundations’ engineering requires at least one full-scale load test on each project. This test is performed on a sacrificial aggregate pier installed at a location determined by the Engineer of Record.

CNC Foundations also maintains a computer data acquisition system on its aggregate pier equipment. This allows the rig operator to monitor the depth, time, and hydraulic pressure, and to visually verify the placement of the rock in real time as the aggregate pier is installed. Because of this, CNC Foundations’ operators provide full-time quality control for the installation of every aggregate pier.

Additionally, the data collected from the field (both installation logs and load testing) are submitted daily to CNC Foundations’ office. This data is reviewed by an engineer to ensure compliance with the project specifications.

Not sure what geotechnical solution can work for your job? We can help.

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