| Popis: |
The Central Arizona Project (CAP) operates and maintains three (3) 21-foot diameter pre-stressed concrete non-cylinder pipes (PCP) as part of the aqueduct system that delivers almost 1,950 million gallons of Colorado River water per day, to Maricopa, Pinal, and Pima Counties in central and southern Arizona. The pipelines, installed in the late 1970’s, have experienced pre-stressing wire breaks and have been repaired several times since the early 1990’s. The wires have broken primarily due to defects in the wire. One of the pipes, the Centennial Wash Siphon, conveys water beneath Interstate-10 and the Centennial Wash, about 80 miles west of Phoenix, AZ. The siphon is upstream of CAP's first customer turnout, and as such is critical in the aqueduct's conveyance and delivery system. An internal electromagnetic inspection in January 2013 discovered several pieces of the pipe comprising the siphon had many broken prestressing wires, prompting a closer inspection and assessment of the siphon. The case study described herein examines inspections, assessment, monitoring, and subsequent repair using post-tension tendons of the Centennial Wash Siphon. This paper further discusses the ongoing efforts of monitoring, assessing, repairing, and maintenance practices for the largest prestressed concrete pipes in the world. A brief history of the siphons includes manufacturing of the 252-inch diameter prestressed concrete pipes, installation of the pipelines, and early investigations and repairs. The focus of this paper is on the assessment and monitoring since the last repairs in 2006, specifically newer technologies that have emerged to assist CAP in monitoring and making decisions in the repair methods and locations. Relevant points include a discussion on the excavation of the pipes requiring repair, the repair work (post-tension tendons), and maintenance practices. A brief discussion will follow on new technology recently installed in all three of CAP’s prestressed concrete siphons. |
