Tuscon, AZ
Central Arizona Project
Scope/Solutions
The 252 in. dia. concrete pipe is used in siphons to convey water in the Central Arizona Project and is the largest diameter pipe in the world. The pipes have a 19.625 in. thick concrete core and two prestressing wire wraps. Using electromagnetic testing techniques, several noncylinder prestressed concrete water conveyance pipes were identified to have broken prestressing wires. SGH evaluated the failure risk resulting from the loss of prestress, determined pipe repair priorities, and subsequently designed post-tensioning repairs and safe excavation for the repair pipe.
Highlights of SGH’s work include the following:
- Computed the earth load and the load distribution on the pipe using a finite element soil-structure interaction program
- Computed the combined effects on structural safety of internal pressure, dead loads, prestress, and prestress loss as wires break in an area
- Determined the failure risk for the pipe and prioritized repairs for the distressed pipe based on its failure margin and its proximity to cracking, structural damage, and rupture
- Developed a post-tensioning repair design for pipe under 15 ft of soil cover and up to 75 ft of water head
- Computed the maximum safe excavation length under the pipe with broken wires assuming that the pipeline is either empty or full of water
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Project Summary
2005
Completion Date
Solutions
Failure Investigation | Repair & Rehabilitation
Services
Advanced Analysis
Markets
Infrastructure & Transportation
Client(s)
Central Arizona Project
Specialized Capabilities
Buried Infrastructure | Risk & Resilience Assessment
Key team members
Additional Projects
West
Owens Dry Lake Project
SGH specified a system for monitoring and controlling the installation quality without specifying means and methods of construction. Measurements of deflection and flattening demonstrated that the installation met the performance requirements and the pipe is performing well.
West
Waukesha Water Utility Garage and Maintenance Building
The Waukesha Water Utility Garage and Maintenance Building, added in the early 1960s, houses storage and a break room on the first level and an L-shaped parking deck and mechanical rooms on the second level. SGH investigated the cause of leakage, and subsequently designed and oversaw repairs.