UW GIGSS Presentation 2011.02.23

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Presentation by Shannon & Wilson on some geotechnical aspects of the SR 532 Design-Build project in Washington State. Presented to the University of Washington Geotechnical Institute Graduate Student Society on 2/23/2011.

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UW GIGSS Presentation 2011.02.23

  1. 1. SR 532 Widening ProjectStillaguamish River Bridge Replacement Mike Harney, MS, PE Oliver Hoopes, MS, EIT Stan Boyle, PhD, PE Shannon & Wilson February 23, 2011
  2. 2. Outline• Design-Build• SR 532 Widening Project• Stillaguamish River Bridge – Subsurface Conditions – Geotechnical Design – Geotechnical Construction• Summary
  3. 3. Traditional Design-Bid-Build Identify Owner ProjectDesign Plans and SpecificationsTeam Bid Contractor Construct
  4. 4. Design-BuildOwner Identify Project Preliminary Concept Plans RFP / BidContractorD-B Team Design Designer Construct
  5. 5. Why do D-B? Schedule! – SR 532 Typical Project Delivery 36 - 48 Months Design Bid Build Design Build Delivery RFP 25 Months Example: SR 532 Bid •Cut ~1 to 2 years off Design schedule Build •$25 million (35%) under budget Risk
  6. 6. Design Build ExamplesTacoma Narrows ThirdBridge, Tacoma, WA Port Mann Bridge Replacement, Surrey, BC
  7. 7. Design Build ExamplesI-405 Tukwila toEverett, WA Cleveland Innerbelt I-90
  8. 8. SR 532 Widening Project • Increase safety • Reduce congestion • Maintain infrastructure • A better environment• Remove and replace existing 2-lane bridge• New 56-ft-wide bridge: 2 traffic lanes, 2 14-ft shoulders, 4-ft median• Improve horizontal and vertical curvature• Reduce west approach/abutment footprint for wetland mitigation
  9. 9. SR 532 Widening ProjectStillaguamish River Bridge Climbing Lanes New bridge Climbing lanes Turning lanes Sidewalks
  10. 10. WSDOT RFP Concept BridgeRetaining Walls Ground ImprovementBridge Piers
  11. 11. DBT Concept Bridge – As-Built Ground Improvement Bridge PiersRetaining Walls Unreinforced Slopes Reinforced Slopes• Eliminated Walls• Converted Walls to Less-Costly Slopes• Eliminated Ground Improvement• Removed Bridge Pier from the River
  12. 12. Existing Subsurface Information Data Gap? Data Gap? 130 ft bgs Deep enough? from Project RFP, Appendix G1 (GeoEngineers, 2008) Fines content? Interbedded or homogeneous? Plasticity?
  13. 13. Subsurface Explorations
  14. 14. Geotechnical Design: Stillaguamish River Bridge• Liquefaction Susceptibility• Soil Parameters – Liquefied Condition  – Static Condition • Approach Embankments/Abutment Walls – Global Stability  (East Abutment STA 193) – Bearing/Sliding Resistance – Lateral Earth Pressures• Seismic-Induced Lateral Spreading• Drilled Shaft Foundations• Seismic Design Parameters
  15. 15. Generalized Subsurface Profile: Stillaguamish River Bridge UPPER SILT SAND LOWER SILT SAND & GRAVEL Deepest Exploration ~200 feet
  16. 16. Generalized Subsurface Profile: Stillaguamish River Bridge UPPER SILT SAND LOWER SILT SAND & GRAVEL Deepest Exploration ~200 feet
  17. 17. UPPER SILT SANDLOWER SILT SAND & GRAVEL
  18. 18. Effective Stress Seismic Site Response: Estimated Porewater Pressure Ratios, Ru Ru = u/’vo UPPER SILT Residual Strength SAND USED Ru = 0.2 Reduced Strength w/ LOWER SILT Ru = 0.2No ProgressiveLiquefaction PSNL DMOD2000(CH2MHill DSS tests indicate (Kramer, 2009) (CH2MHill, 2009)dilative behavior)
  19. 19. Generalized Subsurface Profile: Stillaguamish River Bridge UPPER SILT Residual SAND Strength LOWER SILT Strength Reduced SAND & GRAVEL Static Strength
  20. 20. Post-Seismic Strength: (psf) UPPER SILT SLIGHTLY SILTY SAND70’ – 80’: used Ru = 0.2, Reduced ’ = 23° LOWER SILT
  21. 21. Upper Silt:Consolidated-Undrained Triaxial Testing (used 32°)
  22. 22. Lenz Pit “Blend”Consolidated-Undrained Triaxial Testing (Series Resulted in Effective Friction Angle of 40°)
  23. 23. Embankment Global Stability STA 193+00 ANALYSISLiquefactionSusceptible Soil
  24. 24. Static Global Stability – No Stone Columns FS < 1.5 N.G.Upper sandy SILTFine SAND interbedded with SILT seamsLower clayey SILTMed. Dense to Dense Silty Fine SAND and Fine Sandy SILTMed. Dense to Dense Sandy GRAVELDense to Very Dense, Gravelly SAND
  25. 25. Post-Seismic Global Stability – No Stone Columns FS << 1.1 N.G.!Upper sandy SILTFine SAND interbedded with SILT seamsLower clayey SILTMed. Dense to Dense Silty Fine SAND and Fine Sandy SILTMed. Dense to Dense Sandy GRAVELDense to Very Dense, Gravelly SAND
  26. 26. Post-Seismic Global Stability – With Stone Columns FS > 1.1 O.K.! Stone Columns in SILTUpper SILT Stone Columns in SANDFine SAND interbedded with SILT seamsLower clayey SILTMed. Dense to Dense Silty Fine SAND and Fine Sandy SILTMed. Dense to Dense Sandy GRAVELDense to Very Dense, Gravelly SAND
  27. 27. Static Global Stability – With Stone Columns FS > 1.5 O.K.! Stone Columns in SILTUpper SILT Stone Columns in SANDFine SAND interbedded with SILT seamsLower clayey SILTMed. Dense to Dense Silty Fine SAND and Fine Sandy SILTMed. Dense to Dense Sandy GRAVELDense to Very Dense, Gravelly SAND
  28. 28. Drilled Shaft Foundations
  29. 29. Drilled Shaft Foundations
  30. 30. Drilled Shaft Foundations
  31. 31. Stone Column Ground Improvement Stone Columns Sheet Pile Shoring Existing SR 532 Roadway and Bridge Piers
  32. 32. Stone Column Ground ImprovementPurpose• Mitigate liquefaction-induced instability of abutments – within 100-ft of bridge (thicker cohesionless deposits)• Achieve target static FS of MSE walls (surficial silt)
  33. 33. Stone Column Ground Improvement Surficial SiltLiquefactionSusceptible Soil
  34. 34. Stone Column Ground Improvement Secondary ColumnsPrimaryColumns
  35. 35. Stone Column Ground ImprovementDual Specification• DENSIFICATION in cohesionless, liquefaction-susceptible deposits: Performance-based spec• REPLACEMENT in shallow silt deposit: Prescriptive spec
  36. 36. Stone Column Ground Improvement Performance Specification Densification Target CPT-Equivalent SPT N60
  37. 37. Stone Column Ground Improvement “Unit” Cell Prescriptive Specification Required Composite Ф’ = 40° Secondary Silt: Ф’ = 34° 8 ft Column Dia. = 45” Aggregate: Ф’ = 50° Area Replacement Ratio = 37% Primary Column Diameter = 48”
  38. 38. Stone Column Ground Improvement Primary Columns – Liquefaction Mitigation Secondary Columns – Replace Silt
  39. 39. Stone Column Ground Improvement Dry Bottom-Feed MethodHopper Tremie Tube TremieProbe Vibro-Probe Skip Bucket
  40. 40. Stone Column Ground ImprovementProbe is vibrated as stone flowsthrough the tremie to densify loosesoil and work stone into ground.
  41. 41. Stone Column Ground Improvement
  42. 42. A messy business
  43. 43. A messy business
  44. 44. Stone Column Ground Improvement Containment berm
  45. 45. Elevated Pore Water Pressures?
  46. 46. Stone Column Ground Improvement Sand boils
  47. 47. Stone Column Ground Improvement Air migration
  48. 48. Verification by CPTs
  49. 49. Verification by CPTs
  50. 50. Approach MSE Walls and RSS
  51. 51. Approach MSE Walls and RSS
  52. 52. Approach MSE Walls and RSS
  53. 53. Approach MSE Walls and RSS
  54. 54. Approach MSE Walls and RSS
  55. 55. Approach MSE Walls and RSS
  56. 56. Approach MSE Walls and RSS
  57. 57. Approach MSE Walls and RSS
  58. 58. Summary• Design-Build Project Delivery • Creative, Innovative Engineering • Opportunity to work with Contractor• Application of Concepts from Curriculum • Site characterization and lab testing • Geotechnical earthquake engineering • Stability analyses, walls, ground improvement• Successful Project!
  59. 59. Questions

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