Event

AEG OR Chapter September 19, 2017 Meeting

The Sheep Creek Bridge versus the Sheep Creek Landslide

PURCHASE OF TICKETS USING BROWN PAPER BAG: Ticket sales stops by 5pm on Monday September 18th.

(At the door payments in Cash or Checks only.)

6:00 Social Hour
6:45 Dinner (Salad and Pizza)
7:30 Presentation

PRESENTATION:

Speakers: Philip Wurst (Geotechnical Engineer with ODOT Region 2)

ABSTRACT:

The Sheep Creek Bridge is on Highway US20 in the Cascade Range west of Tombstone Pass. The existing bridge was built in 1963 to replace a timber structure. The east end of the bridge is founded on an active margin of the Sheep Creek Landslide. The slide is about 7,200 feet long by 1,200 feet wide and has about 1,250 feet of elevation relief between the toe and head of the slide. Landslide movement had historically been accommodated by jacking the superstructure back into position across the top of the east abutment. Damage to the abutment required modification of the abutment in 1993 and 2007. Between 2014 and 2015 the slide movement accelerated and all of the slack in the system to allow for jacking had been consumed. The bridge had become stuck between an immovable object (rock promontory) at the west abutment and an irresistible force (the landslide) at the east abutment. Knowing that we could not realistically stop a landslide this big, mitigation to deflect a small portion of the slide away from the end of the bridge was designed. This consisted of a row of heavy, wide flanged, steel beams installed in drilled shafts to act as shear (aka moment) piles placed just uphill of the east abutment in the summer of 2015. This bought us time to design a more permanent solution. In 2016 the highway was closed for six weeks, the eastern portion of the bridge demolished, a deep rock-filled shear key installed in front of the piles, and the east end reconstructed to provide room for future jacking (if necessary). The system was instrumented to monitor performance during construction and to evaluate the future success of the project.

SPEAKER BIO: (Not currently available)