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Undermining of Spillway Chutes

Undermining of Spillway Chutes

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ASDSO Dam Safety 2010 Presentation Presentation Transcript

  • 1. UNDERMINING OF SPILLWAY CHUTES Greg Paxson, PE Jeremy Young, PE ASDSO DAM SAFETY 2010 SEATTLE, WASHINGTON September 22, 2010
  • 2. Presentation Outline
    • Chute Components
    • Modes of Failure
    • Undermining Prevention Measures
    • Case Histories
    • Inspection and Detection
    • Prevention and Rehabilitation
  • 3. Chute Components
          • Control
          • Section
    Cutoff Chute Slabs Drainage Foundation (Soil or Rock) Stilling Basin Joints
  • 4. Modes of Failure - Trojanowski High Velocity Flow
    • Structural Collapse
    • Hydraulic Jacking
  • 5. Failure Modes - Trojanowski High Velocity Flow – Open Joint
  • 6. Failure Modes - Trojanowski High Velocity Flow – Offset Joint
  • 7. Other Failure Modes Inadequate Filtering
  • 8. Other Failure Modes Inadequate Cutoff/ Excessive Seepage
  • 9. Undermining Prevention Measures Staged Filter Waterstop Dowel Cutoff for Joint Support and Drain Isolation
  • 10. Case Histories – PFBC Dams
    • PA Fish and Boat Commission
    • 2004 Failure at Dutch Fork Dam
    • Recent Focus on Spillway Capacity and Potential Spillway Undermining
  • 11. Case Histories – PFBC Dams
  • 12. Colyer Lake Dam
    • Design: 1964
    • Construction : 1966
    • Spillway founded on soil and rock
    • Spalled and cracked concrete
    • Open joints
    • Loss of drainfill
  • 13. Colyer Lake Dam – Cracked Spillway
  • 14. Colyer Lake Dam – Loss of Drainfill
  • 15. Colyer Lake Dam – Ongoing Rehab Design
    • Lake Lowered in 2002
    • Inadequate Spillway Capacity
    • Spillway Coring Program – 6” Voids
    • Undermining due to poor upstream cutoff and suspect joint details
  • 16. Colyer Lake Dam – Upstream Cutoff
  • 17. Colyer Lake Dam – Joint Detail
  • 18. Colyer Lake Dam - Drainage Detail
  • 19. Speedwell Forge Lake Dam
    • Design: 1964
    • Construction : 1966
    • Spillway founded on soil
    • Some history of seepage
    • No observed concrete damage
  • 20. Speedwell Forge Lake Dam
    • Ongoing Rehab Design
      • Inadequate Spillway Capacity
      • Spillway Coring Program – No Voids
      • Video Inspection – Gravel in drains and at outlets
      • Potential Undermining due to suspect joint details
  • 21. Speedwell Forge Lake Dam – Joint Detail
  • 22. Speedwell Forge Lake Dam – Endsill Detail
  • 23. Leaser Lake Dam
    • Design: 1969
    • Construction : 1970
    • Spillway founded on soil and rock
    • Observed concrete deterioration
    • Open Joints
    • Embankment Seepage
  • 24. Leaser Lake Dam
    • Rehab Design
      • Inadequate Spillway Capacity
      • Lake Lowered 1999
      • Spillway Coring Program and GPR Survey
      • Voids identified beneath spillway
      • Undermining due to poor upstream cutoff and suspect joint details
  • 25. Colyer Lake Dam – Weir Detail
  • 26. Colyer Lake Dam – Joint Detail
  • 27. Colyer Lake Dam – Drain Detail
  • 28. PFBC Dams – Proposed Rehabs
    • Colyer Lake Dam
      • Spillway Replacement (in kind)
      • RCC Armoring
    • Speedwell Forge Lake Dam
      • RCC Armoring
      • Spillway Slab Replacement (possible)
    • Leaser Lake Dam
      • Spillway Replacement – Labyrinth
      • Embankment Seepage Control
  • 29. PFBC Dams – Comparison Colyer Speedwell Leaser Year Constr. 1966 1966 1970 Upstream Cutoff No Yes No Joint Support Yes No Yes Waterstop No No No Cutoff No No Yes Adequate Filter No No No
  • 30. Other Case Histories
    • Township Line Dam, West Chester, PA
    • Stoney Creek Dam, Bedford, VA
    • Youngman Dam, Williamsport, VA
    • Big Creek Lake Dam, Mobile, AL
  • 31. Township Line Dam Stoney Creek, VA
    • Design: 1933
    • Construction : 1935
    • Spillway founded on soil
    • Observed concrete deterioration
    • Significant undermining
    • 1993 Grouting Program
  • 32. Township Line Dam – Spillway Deterioration
  • 33. Township Line Dam – Spalled/Offset Joint
  • 34. Township Line Dam – Cutoff Detail Design As-built
  • 35. Township Line – Rehab Design
    • Initially proposed replacement of spillway slabs and installation of drains
    • Supplemental coring program to support final design revealed …
    • Alternate design
      • Grouting voids
      • Spillway overlay (not bonded to existing slabs)
  • 36. Stoney Creek Dam Bedford, VA
    • Construction : 1954
    • Spillway founded on soil
    • Observed concrete deterioration
    • Significant undermining
    • 1987 Grouting Program
  • 37. Stoney Creek Dam – Spillway Deterioration
  • 38. Stoney Creek Dam – Offset Joint
  • 39. Stoney Creek Dam – Joint Detail
  • 40. Stoney Creek Dam – Drain Detail
  • 41. Stoney Creek
    • Rehabilitation Design
      • Install Sheet Pile Cutoff and Replace Control Section
      • Replace Concrete Sideslopes with Vertical Training Walls
      • Remove/Replace Existing Slabs and Drainage Material at Each Joint
      • Concrete Overlay
      • RCC Embankment Armoring
  • 42. Youngman Dam Williamsport, PA
    • Construction: 1951
    • Spillway Founded on Rock
    • Observed Spillway Seepage and Open Joints
    • Inadequate Spillway Capacity
    • `
  • 43. Youngman Dam – Rehab Design
    • Spillway Coring Program and GPR Survey
      • 3 inch voice
    • Video Inspection of Drainage System
      • Clogged Underdrains
    • Undermining due to suspect joint details and poor joint locations
  • 44. Youngman Dam – Joint Detail
  • 45. Youngman Dam – Weir Detail
  • 46. Youngman Dam – Rehab Design
    • Grouting selected chute slans
    • Selected joint replacement and drain installation
    • Joint Sealant
    • Rehab Joint and drain at base of ogee
      • Joint Sealant
      • Relief Drains
      • Chute Blocks
  • 47. Youngman Dam – Ogee Rehab
  • 48. Big Creek Lake Dam Mobile, AL
    • Design: 1947
    • Construction: 1952
    • Spillway Founded on Soil
    • History of Undermining and Sinkholes
    • Inadequate Chute Capacity
    • Slab failure following routine release in 2005
    • `
  • 49. Big Creek Lake Dam – 2005 Sinkhole
  • 50. Big Creek Lake Dam – Loss of Drainfill 2005
  • 51. Big Creek Lake Dam – Open Joint 2005
  • 52. Big Creek Lake Dam – Undermining 2005
  • 53. Big Creek Lake Dam – Joint Detail
  • 54. Big Creek Lake Dam – Rehab
    • Emergency Response
      • Filled Voids w/ Sand and Grout
      • Temp Stabilized Slabs w. Soil Anchors
    • Contract No. 1 – Vertical Anchors
    • Contract No. 2 – Dividing Chute Wall
    • Contract No. 3 – Spillway Walls and Stilling Basin Rehab
    • Contract No. 5 – Spillway Overlay and Overbank Armoring
  • 55. Big Creek Lake Dam – Slab Rehab
  • 56. Big Creek Lake Dam – Overview
  • 57. Inspection and Detection
    • Review original design drawings for suspect details
    • Visual inspection
    • Video inspection of drainage system
    • GPR survey
    • Spillway coring program
  • 58. Visual Warning Signs
    • Cracking and settlement
    • Drainage/foundation material in drain pipes
    • Offset or open joints in drain pipes
    • Offset or open joints (w/o waterstop) in chute
    • Seepage flowing into a slab joint
  • 59. Suspect Joint Details
    • Lack of waterstop and dowels
    • Lack of cutoff and adequate slab support
    • Inadequate filtering of drain material
    • Shallow upstream cutoff
    • Poor location/orientation of joints
  • 60. Prevention
    • Waterstops at each joint
    • Cutoffs at each joint for slab support and to isolate seepage
    • Dowels to prevent offset joints
    • Adequately designed underdrain system (capacity and filter criteria)
    • Adequate upstream cutoff to control seepage through foundation
  • 61. Rehabilitation
    • Grouting voids beneath spillway
    • Constructing a concrete overlay
    • Joint sealant in open joints
    • Repairing spallled and offset joints
    • Rehab chute joints
      • Deeper cutoffs and/or adequate filter
    • Anchoring chute slab
  • 62. Acknowledgements
    • Jerry Woomer and the PA Fish and Boat Commission
    • Aqua Pennsylvania
    • The City of Bedford, Virginia
    • Williamsport Municipal Water Authority
    • Mobile Area Water and Sewer System
  • 63. Questions? UNDERMINING OF SPILLWAY CHUTES Greg Paxson, PE Jeremy Young, PE ASDSO DAM SAFETY 2010 SEATTLE, WASHINGTON September 22, 2010