Close-in blasting at the TRI-MET light rail tunnels in Portland, Oregon

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:400798

Revey, G F; Painter, D Z

Frontier/Traylor Joint Venture is presently constructing a section of the Tri-County Metropolitan Transit District of Oregon`s (TRI-MET) Westside Light Rail System. This new section will extend Portland`s existing transit system to the western suburbs of Beaverton and Hillsboro. The drill-blast excavations at this project include 10,000 feet of 20 foot tunnel, 18 cross passages, three shafts, an underground railway station, and a U-wall open cut. From a blast designer`s perspective, this job has been extremely challenging. Blast vibration is limited to 0.5 ips at 200 feet or at the nearest structure, and airblast is limited to 129 dB--linear peak and 96 dB--C scale. The tunnels pass under heavily built up areas and have top of tunnel to surface cover distances as low as 70 feet. Surface blasting in the 26,000 cubic yard U-wall excavation was limited to five short nighttime periods due to its proximity to the very busy highway 26. This paper describes the techniques that were used to develop safe blasting designs for the TRI-MET Surface blasts and tunnel rounds. It also discusses the measures that were necessary to mitigate noise, vibration, and flyrock.

• OSTI ID: 400798
• Report Number(s): CONF-950247--
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
CONSTRUCTION
DESIGN
EXPLOSIVE FRACTURING
GROUND MOTION
LIMITING VALUES
MASS TRANSIT SYSTEMS
OREGON
RAILWAYS
ROCK DRILLING
SAFETY ENGINEERING
SHOCK WAVES
TUNNELS