Natural Hazards Large and Small

Transcription

1 Specialty Seminar on Engineering of Geo-Hazards ASCE Met Section Geotechnical Group and Geo-Institute of ASCE 16 May 2007 Natural Hazards Large and Small Evaluation and Mitigation Edward Kavazanjian, Jr., Ph.D., P.E. Arizona State University 1

2 OVERVIEW Geologic Hazard Mitigation Long a Part of Geotechnical Practice Enhancing Resilience to Extreme Events Increasing Importance due to Urbanization, Complexity 2

3 Geologic Hazard Mitigation Slope Stability Swedish Circle Method circa 1910 Compressible Soil Settlement Terzaghi circa

4 Slope Failure in Sweden 4

5 Enhancing Resilience Increased Susceptibility due to: Increasing Urbanization 49% of World Population Urbanized in % of World Population Urbanized in 2050 Most Development in Coastal Areas Increasing Complexity Interdependence of Infrastructure Systems Global Economy 5

6 Enhancing Resilience Increased Impacts of Large and Small Events Indirect Economic Impacts Often Surpass Direct Damage Loma Prieta / Northridge / Kobe Earthquakes December 2005 Tsunami Hurricane Katrina 6

7 1989 Loma Prieta Earthquake Direct Damage: $ 5 Billion Indirect Damage: $10 Billion 7

8 Damage from Major Disassters 8

9 Damage Trends 9

10 Geologic Hazards Small, Persistent Geologic Phenomenon Local Geologic Features Small Details Causing Large Singular Events Regional Geologic Phenomenon Multiple Events Extreme Events 10

11 Small, Persistent Phenomenon Large Cumulative u Effects Over Time Soil Erosion Soil Loss, Sedimentation, Air and Water Pollution Soil Creep Structural Damage Reactive Soils Corrosion, Sulfate Attack 11

12 Local Geologic Features Thin Weak Seams, Bedding Planes Slope Stability Faults, Fracture Zones Stability, Underground Construction 12

13 Impact of Small Geologic Details A Persistent Theme in Slope Stability Ml Malpasset and Vajont Vj Dams 13

14 Ocean Trails Landslide (2001) Known Landslide Terrain Project Site 14

15 Ocean Trails Cross Section 15

16 Ocean Trails Consequence 16

17 Katrina 17 th Street UCB Hypothesis 17

18 Regional Geologic Phenomenon Expansive Soil Collapsible Soil Compressible Soil Karst Terrain 18

19 Expansive Soils in the U.S. Estimated Impact > $10 Billion per year! 19

20 Regional Subsidence Wilmington Settlement Bowl: Note: Settlement Contours in Feet 20

21 Extreme Events Earthquakes Floods Tsunamis Wind Storms Scour 21

22 Schoharie Creek Bridge Failure 17 April people died 22

23 Hurricane Katrina Most Damaging Geotechnical Failure in U.S. History 23

24 Geological Hazard Mitigation Four Step Process Identify Analyze Assess Mitigate 24

25 Identify Geologic Conditions Creating the Hazard External Events Triggering the Hazard 25

26 Analyze Potential for Triggering the Hazard for a Specified Loading Factor of Safety or Probability bilit of Failure Loading Level that Triggers the Hazard Yield Condition or Probability of Occurrence 26

27 Assess Assess Consequences of Triggering the Hazard (Failure) May Want to Consider Worst Case Scenario Avoid Over-Reliance on (Over Confidence in) Analysis Redundancy and Ductility Reduce Impacts, Enhance Reliability 27

28 Mitigate Evaluate Cost / Benefit of Mitigation Measures Structural Measures Mitigation i i not Always Feasible or Cost Effective Non-Structural Measures Often Most Cost-Effective May Not be Politically Palatable 28

29 Geo Hazard Mitigation State of Practice 1989 NRC Report Recommendations for Improving Geotech Practice for Hazard Mitigation i i 2006 NRC Report Progress Since 1989 Unresolved Issues and Opportunites for Improvement 29

30 1989 NRC Report Recommendations Geotechnology: Its Impact on Economic Growth, the Environment, and National Security Recommendations Better Land Use Planning Increased Use of State-of-the-Art Analysis Incorporation of Risk Assessment More Large Scale Research 30

31 2006 NRC Report Findings Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation* * Progress from Development of Regional Hazard Maps Slope Stability, Liquefaction, Flood Use of S-O-A Analysis Has Increased Continued Emphasis Warranted Increased Use of Reliability Little Formal Risk Assessment Increase in Large Scale Research I-15, NGES, NEES 31

32 2006 NRC Report Findings Geotech Knowledge Gaps Ability to See Into the Earth Improved Sensors and Sensing Characterization of Spatial Variability and Uncertainty Less Expensive, More Effective, Less Disruptive Soil Stabilization and Ground Improvement 32

33 2006 NRC Report Findings Ability to See into the Earth: Geophysics! 3-D Radar Tomography, West Palm Beach, FL (Witten Technologies, Inc.) 33

34 2006 NRC Report Findings Non-Intrusive Ground Improvement: Bio-Improvement? Calcium Carbonate Precipitation by Microbial Hydrolysis of Urea Mitigate Liquefaction Potential by Microbially Induced Cementation? 34

35 2006 NRC Report Findings Advance Technology for Hazard Mitgation Automated Landslide Warning Systems TDR, In Place Inclinometers Remote Sensing InSAR, LIDAR Advanced Photogrammetry High Resolution Aerial Photography GIS Technology GPS, PDAs 35

36 Automated Landslide Warning Systems Colorado Springs Monitoring System, Overton, et al. (2004) 36

37 InSAR Space Borne Remote Sensing Phoenix Area Subsidence due to Northridge Earthquake Tectonic Groundwater Extraction Displacements (Tatlow and Buckley, 2003) (Pelzer, 2003) 37

38 LIDAR Pikes Peak Topography Source: Merrick and Company 38

39 GIS Applications Hong Kong Landslide Mobile Mapping System 39

40 Non-Structural Hazard Mitigation Measures Land Use Planning Hazard Mapping Zoning Disaster Preparedness Warning Systems Contingency Planning Emergency Response Recovery Plans 40

41 Public Policy Issues Land Use Planning Emergency Planning Reserch and Development 41

42 Land Use Planning Social and Political Implications Often Dominate the Debate Dissuade Engineers From Participating 42

43 Emergency Planning Practice Makes Perfect Need to Consider System Performance Redundancy and Ductility Create Resilience May Require Public Investment in an Era of Spending Limits, No New Taxes Engineers Must Inform the Debate 43

44 Research and Development Return on Investment is Clear Success of Earthquake Hazard Mitigation Efforts Public Will to Invest is Lacking Must Communicate Benefits Better 44

45 CONCLUSIONS Geologic Hazard Mitigation an Essential Part of Geotechnical Practice Susceptibility to Hazards in Constantly Increasing Both Structural and Non-Structural Mitigation Measures Must be Considered Advanced Technologies Offer Great Advantages Non-Structural Measures May Still be Most Reliable and Cost Effective Increased Investment in Geologic Hazard Mitigation is Needed Engineers Must Participate in the Political Process 45

46 Questions? 46