Joint AEG Nisqually and ASCE Tacoma-Olympia Section April 2020 Meeting:
The joint meeting is in Tumwater at the Pellegrino's Event Center, 5757 Littlerock Rd SW Tumwater 98512 www.PellegrinosEventCenter.com
The social starts at 6:00pm, dinner at 7 and the presentations at 7:30pm.
Dinner is your classic Italian menu, salad, meat and pasta. Contact your chapter chair to reserve for special diets.
Two great talks by two local geologists: Eric Smith and Susan Schnur.
Eric's talk is: What If the Rock Only Threatens to Fall? Emergency Response to a Decoupled Cliff Face in Washington State
Susan's talk is the WA100, A Washington Geotourism Website.
Eric's abstract: Many engineering geologists are familiar with the following scenario: hundreds of cubic yards of rock debris have blocked a roadway, with resultant disruption to traffic and commerce. Assessment is necessary to evaluate whether additional unstable rock material remains on the slope and whether the debris on the roadway can be safely cleared in order to reopen (or partially reopen) the road. What if, however, instead of hundreds of cubic yards, the event included several thousand cubic yards of material, all within a single rock slab, which suddenly decoupled from the rock face, and essentially teetered above the roadway? Such an event occurred on Washington State Route 503 during the spring of 2017. A single slab of volcanic rock (measuring approximately 65 to 70 feet tall, 100 to 105 feet wide and 15 to 20 feet thick) suddenly detached from a vertical cliff face upslope of the highway, dropped approximately 15 feet, and came to rest in a precarious sub-vertical position on a highway-sloping bench. The subsequent WSDOT emergency response included highway closure/detour, geologic and UAV (drone) reconnaissance, terrestrial LiDAR scans and change analyses, exploratory drilling, and emergency rock scaling and trim blasting. A follow-on design and bid contract included additional scaling and trim blasting, and the installation of rock reinforcement and horizontal drains in unstable areas behind and adjacent to the failure site. The combination of geologic, topographic and hydrogeologic factors that led to this failure include: competent volcanic rock overlying weaker volcaniclastic rock; a highly persistent sub-vertical rock discontinuity set; steep to moderately-sloping upland terrain above the highway-adjacent cliffs; perched groundwater; and a mineral assemblage within the volcaniclastic that is vulnerable to localized differential weathering. This presentation will highlight how these site conditions are informative to geohazard specialists working in volcanic terrain.
Pellegrino's Catering & Event Center (View)
5757 Littlerock Rd SW
Tumwater, WA 98512
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