CDOT Sign Hole utilizing flow fill technique
CDOT project for a sign hole along Interstate 70 in Colorado, Drilled Shafts, Length - 30 ft., Diameter - 48 in.
General Contractor and Owner:
Sturgeon Electric, CDOT (Colorado Department of Transportation)
Due to the large cobbles and the job into in the center median of a major artery, I-70 west of Denver, temporary casing was not an option. The Flow Fill technique was essentially the only method adequate to avoid cave-ins along the entire length of the shaft. The pictures show the very limited access afforded this project as well as the size of the cobbles encountered. The technique calls for drilling a short distance, fill the hole with Flow Fill or lean (2500 psi) concrete, letting it cure over night, drilling through that pour and an additional distance, and repeating the process until the desired depth is reached. Typically, we can advance about 5 feet per day. The result is a clean, rough, non-caving shaft. It takes additional time to perform this procedure, but it is the only viable solution and Ludwig Drilling is expert in its use.