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8 DEFINITIONS The following definitions were provided in the preamble to the questionnaire sent to the state DOT geotechnical leaders: ⢠Hazard: Condition or situation with the potential to cause harm. ⢠Disaster: Outcome of a hazard when it changes from potential event to actual event. ⢠Geotechnical Data Visualization: Viewing and/or ana- lyzing geotechnical data using visual software. The following additional definitions are provided to clar- ify terms used in this report: ⢠Natural phenomena hazard: A natural condition or extreme event that may threaten a transportation system. ⢠Geotechnical hazard: A threat attributable to the soil, rock, and/or groundwater beneath or adjacent to a trans- portation system. ⢠Geotechnical hazard mitigation: Identification, moni- toring, design, and construction of mitigation measures for a geotechnical hazard. ⢠Geotechnical disaster response: Immediate and short- term response to a geotechnical event to assist in rescue efforts, protect public and worker safety, and reduce transportation system delays or detours. ⢠Geotechnical disaster recovery: Long-term recovery from a geotechnical event to restore public safety and transportation system functionality. Several systems of classifying natural phenomena haz- ards have been proposed. For example, the Organization of America States (OAS) has proposed the classification system shown in Table 1 (http://www.oas.org/dsd/publica tions/Unit/oea54e/ch05.htm) and the Centre for Research on the Epidemiology of Disasters (CRED) in Europe has pro- posed the system shown in Table 2 (http://www.emdat.be/ classification). Although each of these systems has its pur- poses and advantages, for report purposes it is simpler to classify natural phenomena hazard origins as geological or meteorological (including climatologic and hydrologic sources) because geotechnical hazards may arise from mul- tiple natural phenomena hazards: For example, an unstable slope may arise from seismic activity (geological origin) or extreme precipitation (meteorological origin). The survey of state DOT geotechnical leaders indicates that as many as 90% of the geotechnical disasters they have encountered are the result of meteorological events. Geotechnical hazards can be naturally occurring condi- tions (e.g., unstable slopes or soft soils) or can arise from the constructed features of a transportation system (embankment fills or cut slopes, etc.). The most commonly encountered geo- technical hazards are summarized in Table 3. This table also identifies the potential origin(s) of the geotechnical hazard. Although the hazards may vary from state to state, and even region to region within a state, the effective use of GDV tools and methods in one location can be expected to apply to a range of conditions, events, and objectives in another location. The following are several examples of natural phenomena that have led to geotechnical disasters and damage to trans- portation systems. EXAMPLES OF NATURAL PHENOMENA Landslide, Oso, Washington, March 2014 The landslide disaster of March 22, 2014 near Oso, Wash- ington (Figure 2), cost more than 40 lives, temporarily dammed the Stillaguamish River, and blocked Washington State Route 530. The landslide occurred after a period of unusually intense rainfall, but the specific causes of the land- slide are still under investigation. A U.S. Geological Survey (USGS) website (http://www.usgs.gov/blogs/features/usgs_ top_story/landslide-in-washington-state/) has several other examples of GDV for this disaster. In addition to a lidar (light detection and ranging) image similar to the one shown in Figure 2, the website has a video of a landslide runout model and seismograph records used to confirm that the landslide was not caused by an earthquake. While use of high resolu- tion lidar images and other visualization techniques would not change the need to route a highway through this valley, the newer images will likely improve the understanding and perception of risk to lives and infrastructure. Rockfall, Thermopolis, Wyoming, 2002 The rockfall on a railway embankment shown in Figure 3 occurred after spring runoff eroded the soil underlying a tufa formation. Note the ties and rails in the right-center of the chapter two HAZARDS, DISASTERS, AND EXTREME EVENTS
9 Category Hazard Examples Atmospheric Hailstorms, hurricanes, lightning, tornadoes, tropical storms Seismic Fault ruptures, ground shaking, landslides, lateral spreading, liquefaction, tsunamis, seiches Other Geologic or Hydrologic Debris avalanches, expansive soils, landslides, rockfalls, submarine slides, subsidence Hydrologic Coastal flooding, desertification, salinization, drought, erosion and sedimentation, river flooding, storm surges Volcanic Tephra (ash, cinders, lapilli), gases, lava flows, mudflows, projectiles and lateral blasts, pyroclastic flows Wildfire Brush, forest, grass, savannah TABLE 1 HAZARD CLASSIFICATION SYSTEM (OAS) Hazard Subgroup Definition Hazard Main Type Geophysical Events originating from solid earth Earthquake, volcano, mass movement (dry) Meteorological Events caused by short-lived, small to meso-scale atmospheric processes (in the spectrum from minutes to days) Storm Hydrological Events caused by deviations in the normal water cycle or overflow of bodies of water caused by wind set-up Flood, mass movement (wet) Climatological Events caused by long-lived, meso- to macro-scale processes (in the spectrum from intra-seasonal to multi-decadal climate variability) Extreme temperature, drought, wildfire TABLE 2 HAZARD CLASSIFICATION SYSTEM (CRED) Hazard Hazard Origin Natural phenomena Human action Geological1 Meteorological2 Slopes (natural or cut) x x x Embankments x x Slope Creep x x x Rockfalls x x x Avalanches x x x Debris Flows x x x Settlement or Heave x x x Sinkholes x x x Subsidence x x x Lateral Spreading x Liquefaction x Surface Ruptures x Frost Heave x Permafrost Thaw/Freeze x Frozen Debris Lobes x x Tsunamis x Seiches x x Storm Surge x Wind Blown Soil/Dunes x x 1Earthquakes, volcanoes. 2Includes hydrological and climatological phenomena. TABLE 3 GEOTECHNICAL HAZARDS
10 photograph that were pushed off the embankment by the rockfall. A better understanding of the local geology and seasonal groundwater conditions might have led to hazard mitigation measures that could have avoided this disaster. Earthquake Sand Boils, Seattle, Washington, February 2001 Among the many consequences of the February 28, 2001, earthquake centered near Nisqually, Washington, was the appearance of sand boils on King County International Air- port (aka Boeing Field) taxiways and runways. Liquefied sand was ejected through pavement joints and cracks opened by the 6.8 (moment magnitude scale) earthquake as shown in Figure 4. The sand boils occurred in limited areas on the taxiway, runway, and in adjacent grass-covered areas, indi- cating that liquefiable soils in the airport subgrade may be isolated. The airport is built on a former river floodplain, which may have buried channels of liquefiable soils that led to the limited sand boil area. Although the airport area is almost entirely paved, air photographs from areas upstream of the airport indicate the presence of buried former river channels. Debris Flows, Beartooth Highway, Montana, May 2005 A spring rain-on-snow event in the Beartooth Mountains of eastern Montana resulted in massive debris flows that dam- aged 13 locations on the steep hairpin highway leading to an eastern entrance to Yellowstone Park. Figure 5 shows two of the damage locations (note the damage to the upper switch- back near the top of the photograph). Because this highway provides access to the park and is critical to local economy, a design-build team was awarded a contract to restore the highway in a single construction sea- son rather than using a traditional design-bid-build contract that might have taken more than two years to complete. GDV tools played a critical role in rapid assessment, design, and construction of the repairs. The primary visual- ization tools were air photography and the visualization fea- tures of the stability and retaining wall design tools used by the team. Design and construction was a dynamic process: FIGURE 2 Landslide, Oso, Washington, March 2014. (Image credit: Puget Sound Lidar Consortium, 2013.) FIGURE 3 Rockfall, Thermopolis, Wyoming, 2002. (Photo credit: D. McCulloch.) FIGURE 4 Nisqually Earthquake, February 2001, sand boils, Boeing Field Taxiway, Seattle, Washington. (Photo credit: M. Anderson.)
11 Concepts were developed, designs advanced, equipment mobilized, and materials ordered as explorations, excava- tions, and construction were in progress. Repairs were com- pleted in four months at an estimated savings of $6 million. Landslide and Debris Flow, Bonners Ferry, Idaho, October 1998 The following description of the geotechnical disaster that damaged two roads and a railroad is from the National Oce- FIGURE 5 Debris flow, May 2005, Beartooth Highway, Montana. (Photo credit: Montana Department of Transportation.) FIGURE 6 Landslide, October 1998, Bonnerâs Ferry, Idaho. (Photo credit: D. Krammer, Disaster Services, Boundary County, Idaho.) anic and Atmospheric Administrationâs National Geophysi- cal Data Center (http://www.ngdc.noaa.gov/hazardimages): On October 15, 1998, more than 200,000 [cubic yards] of mud gushed out of North Hill. It covered up a county road, and destroyed a portion of Union Pacific track and a 200-yard area of Highway 95. The mass of mud buried almost one million dol- lars worth of equipment. Note the rails still suspended in air after the collapse of material beneath them. Highway 95, Idahoâs only major north-south route, was closed [for] three weeks because of the slide. The buried equipment was being used to cut into the toe of slope. The cut exposed saturated, soft and loose, prehistoric glacial lake sediments which are seen in the debris runout in the lower part of the photograph in Figure 6.
