Inspection of the Glen Canyon Dam Access Tunnel in Page, Arizona

摘要

The Glen Canyon Dam Access Tunnel, owned by the United States Bureau of Reclamation (USBR), is a two mile long, 24-ft high, and 22-ft wide horseshoe shaped tunnel located in Page, Arizona. The tunnel was completed in 1958 and was driven through massive Navajo Sandstone by the drill-and-blast method. The tunnel has limited access and is used by the USBR on a daily basis to access the Power Plant at the base of the dam. Summertime sees an increase in daily traffic by commercial Whitewater rafting enterprises using the tunnel to access the Colorado River. The paper describes the on-site inspection of the tunnel to document the physical and functional conditions of the tunnel structure. The approach to the inspection and documentation of results was based on methods described in the Federal Highway Administration (FHWA) Tunnel Operations, Maintenance, Inspection, and Evaluation (TOMIE) Manual. The inspection team performed an in-depth inspection, including full arch periphery geologic mapping of the entire tunnel including a cast-in-place concrete section. The inspection included mapping of all rock bolts that appeared deteriorated, loose, or noted to be in poor condition by previous USBR maintenance team inspections. Geologic characterization included mapping structural rock features such as bedding planes, joints, fractures, and faults. All geologic and ground support features were recorded and documented on full periphery mapping sheets. The presentation provides a case history of inspection of a roadway tunnel which includes multiple types of tunnel lining support systems including cast-in-place concrete, structural steel sets and rock bolts.