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]
Geologic Hazards
Landslide on Arizona SR 87 Closes Highway
On March 21, 2008 a landslide caused the closure of Arizona State Route 87 between Payson and Phoenix near mile post 224. So far there are no official estimates as to the size, but based on aerial photos, it appears to be at least 50,000 sq-ft in plan. The offset at the head scarps was approximately 2-meters (6.6-ft) according to AZGS Geologists on site. It appears to have been a rotational slide as the toe of the landslide heaved the southbound roadway up by as much as 1-meter (3.3 ft). There was an existing soil-nail retaining wall on the slope that was destroyed by the slide as well. Lateral deformations can be seen in photos of the median barrier and the roadway striping. The deformations extended into the northbound lanes as well. More photos and links after the break. (Photo by ADOT)
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Available Resources
FHWA NHI Manual: Drilled Shafts Construction Procedures and LRFD Design Methods
The FHWA has released for download a comprehensive update to the 1999 O’Neil and Reese manual “Drilled Shafts: Construction Procedures and Design Methods”, lovingly referred to in the industry as the “Brown Book” or the “Drilled Shaft Bible”. This 2010 manual from the National Highway Institute (NHI) of the FHWA is entitled “Drilled Shafts: Construction Procedures Procedures and LRFD Design Methods” and was authored by Dan A. Brown, Ph.D, P.E. of Dan Brown and Associates, John P. Turner, Ph.D, P.E. of the University of Wyoming, and Raymond J. Castelli, P.E. From an FHWA Memo on the manual:
Distributed with this memorandum is the publication entitled "Drilled Shafts: Construction Procedures and LRFD Design Methods" (FHWA-NHI-10-016). This manual is the reference text used for the National Highway Institute (NHI) course numbered 132014 on Drilled Shafts. The publication will become the tenth in the series of geotechnical engineering guidelines called "Geotechnical Engineering Circulars." Geotechnical Engineering Circular (GEC) No. 10 is prepared as a significant revision and update to "Drilled Shafts: Construction Procedures and Design Methods" (FHWA IF-99-025), and reflects the standard of practice for the design, construction and inspection of these features. The guidance is developed following Load and Resistance Factor Design (LRFD) procedures and will enable engineers to identify and evaluate technical feasibility and potential applications. The text is developed with a sufficiently broad scope to be of value to a wide range of transportation specialists responsible for assisting with selection, design, development of materials specifications, construction monitoring, and contracting methods for Drilled Shafts.
Click through for the download link and some preliminary comments on what has been updated in this significant new publication in the drilled shaft construction industry as well as the geotechnical engineering profession.
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Project Related
Update on Landmark Kansas City Bridge Project – kcICON
Another nice post from Robert Thompson with Dan Brown and Associates (DBA) about the geotechnical work on the kcICON project. They are the geotechnical designers for a $245 million project that will involve a new cable-stayed bridge over the Missouri River in downtown Kansas City along the I-29/35 corridor. In his post, Robert gives an update on the status of the work including the borings and recent test shaft installation and testing as well as an update on the overall project. (Rendering by Paseo Corridor Constructors)