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Event
AEG OR Chapter DECEMBER 2016 Meeting
Idaho Transportation Department (ITD): Emergency Rockfall Assessment, US-95, Riggins, ID, December 2012
PURCHASE OF TICKETS USING BROWN PAPER BAG: Ticket sales stops by 4 pm on Friday Dec. 16th.
(At the door payments in Cash or Checks only.)
6:00 Social Hour
6:45 Dinner (Salad and Pizza)
7:30 Presentation
PRESENTATION:
Speaker: William CB Gates, PhD, PE, PG, PEng
ABSTRACT:
During the evening of 2 December 2012, a large rockslide occurred which blocked US-95 at MP 188 about 5 miles south of Riggins, Idaho. No accidents were reported as a result of the rockslide. The next day, ITD noted a large 200 ton unstable block hanging precariously on the face that required immediate assessment.
The rockslide originated from an ultramafic rock massif cropping out about 250 feet above the road. The team employed rappelling techniques to map vertical scanlines and access the unstable block. While on rappel the team collected physical and engineering characteristics of the rock mass including information on discontinuities. The field data was used to assess the kinematic relationships between the structure of the rock mass and the rockslope face and establish failure mechanisms. During assessment, a large and deep tension fracture was observed between the critical block and the hanging wall of the main rock mass. The kinematic analysis demonstrated that the critical block and slope were unstable and wedge failures were dominant.
To mitigate the initial unstable slope conditions and critical block a rock scaling contractor was immediately mobilized to the site. After assessment, the team established that the block should be removed by trim blasting. The author provided a trim blasting design and worked closely with the blaster-in-charge and contractor to drill, load and shoot the critical block. The block was removed safely by presplit blasting on 23 December. The US-95 highway was then reopened to the public to accommodate the Christmas traffic.
SPEAKER BIO:
Dr. Bill Gates is principal rock engineer with McMillen Jacobs Associates and oversees the rock engineering and blasting program. He is a retired Special Forces Officer, Green Beret, and spent 22.5 years in the Army. After retiring from the Army, he spent 22.5 years with Kleinfelder and retired once more. He has been with McMillen Jacobs Associates for 5 years. He is registered as a professional engineer and geologist in several states as well as British Colombia.
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LocationOld Market Pub (View)
6959 SW Multnomah Blvd.
Portland, OR 97223
United States
Categories
| Kid Friendly: Yes! |
| Dog Friendly: No |
| Non-Smoking: No |
| Wheelchair Accessible: Yes! |
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Contact
| Owner: Oregon AEG |
| On BPT Since: Nov 06, 2016 |
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| Chris Humphrey |
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