ADOT put together a great little video embedded below that shows the construction of a drilled shaft foundation, or caisson as they are also known, for a bridge on the Loop 303 project in Surprise, AZ. The foundations shown are 88-feet deep and the rebar cage weighs in at about 20,000 pounds. The hole takes around 80 cubic yards of concrete to fill (that’s 8 concrete trucks). The video shows the fabrication of the cage, drilling the hole, and picking up and lowering the cage. My favorite part is the perspective of the video taken from the top of the cage as it is picked up and lowered, very cool. [Source: ADOT Blog]
Failures
Drilled shaft rig falls into hole – Iowa
On May 15 a drilled shaft rig operated by Mid America Drilling Corp was nearly swallowed by the 9-ft diameter hole it was drilling for a cell tower foundation near Harlan, Iowa. Fortunately nobody was injured and the truck did not suffer any significant damage.
In Arizona, the standard of practice is to use a temporary surface casing to prevent dangerous failures like that. I once saw pictures of a drilling contractor superindendent almost get sucked into a collapsing shaft, even with the temporary casing. Pretty scary stuff. Source: Harlan Tribune. (Photo by Samantha Bruck)
Miscellaneous
ADSC Lawrenceville Rock Socket Load Test Site–Prediction Contest!
As part of an ongoing ADSC research project on axial capacity of drilled shaft rock sockets in the Southeastern US, several test shafts were constructed this past week and the load test portion will commence […]
Available Resources
ADSC Technical Library Catalog
The Association of Drilled Shaft Contractors or ADSC has a catalog of their technical library available through their website. ADSC has countless useful publications for drilled shaft designers, most of them very reasonably priced for […]