Geology Presentation

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  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • Granite is 500m below surface but piles can only be driven down ?m
  • is granite overlain by 300m of glacial till and 200m of silt and mud, Bridge ends must be anchored in highly-fractured shales that dip toward the water
  • Intermin- unofficial inspection done every 6 monthsDamage inspections- after a collision to the bridge or major environmental changes ie floods, mass movements
  • Black-white fathometer: uses sound waves to detect channel depths however if the scour hole refilled it will not be able to detect itColor Fathometer: diff colors mean diff densities this device works on refilled scour holes
  • Geology Presentation

    1. 1. Suspension Bridge<br />Sadia Khan<br />Terryn Kuzyk<br />Brogan Gordon-Cooper<br />Paul Coutts<br />
    2. 2. PresentationOutline<br />Introduction<br />Geological Setting<br />Bridge Components<br />Engineering Solutions<br />Maintenance<br />Conclusion<br />Tacoma Narrows Bridge<br />
    3. 3. Introduction<br />Structure<br />Suspension Bridge<br />GeologicalSetting<br />Bedrock is granite<br />Bedrock is beneath 300m of glacial till & 200m of silt/mud<br />Ends must be anchored in highly-fractured shale that dips towards the water<br />
    4. 4. Geological Settings<br />Shale<br />Glacial Till<br />Granite Bedrock <br />Unconsolidated Silt and Mud <br />
    5. 5. Shale<br />Lithified Mud<br />Highly Bedded & Fissile<br />Weak Rock<br />Fractured Shale is Permeable & Susceptible to Fluid Migration<br />
    6. 6. Problems with Fractured Shale<br />Water can creep through the cracks increasing weathering of the rock<br />Clay within the shale can expand and contract resulting in slope failure<br />Shale rapidly scours<br />Excavation causes stress release<br />Since it dips towards the water, hydrostatic pressure develops forcing bedding planes apart<br />
    7. 7. Silt and Mud <br />Silt: fine or intermediate-sized particles from various mineral<br />Mud: silt and clay <br />Problems with Silt and Mud <br /><ul><li>Mass movements can occur from saturation</li></ul>Development of quick clays (clays originating from marine environments) <br />
    8. 8. Glacial Till<br />Poorly sorted <br />Primarily angular in nature<br />Contains almost all rock sizes<br />Result of glacial movement<br />
    9. 9. Problems with Glacial Till<br />Unsorted sediment introduces risk of hitting large boulders, which can interfere with construction<br />Mass movements can occur when overriding silt and mud layer starts to slide<br />
    10. 10. Granite Bedrock<br />Extrusive igneous rock consisting of mostly quartz, orthoclase and biotite<br />Relatively hard rock therefore ideal for placing foundation of structures <br />500m below surface (our geological location)<br />
    11. 11. Problems with Granite Bedrock<br />Depth may not be feasible for constructing anchors and piers <br />Excavating hard rocks such as granite may abrade expensive machinery <br />
    12. 12. Suspension Bridge Components <br />Main Cables <br />Hangers <br />Deck <br />Piers <br />Anchors <br />
    13. 13. Engineering Solutions Outline <br />Problems <br />Solutions<br />
    14. 14. Solutions for Anchoring into Fractured Shale <br />Anchor directly into granite bedrock instead of fractured shale <br />Locate anchor in areas with minor fractures in shale <br />Place concrete slab over fractured shale <br />Use rock bolts to restrain fractured rock <br />
    15. 15. Anchoring into Granite Bedrock<br />Granite is an ideal rock to anchor into due to its high compressive strength and lack of bedding <br />Unreasonable solution due to its location at 500m depth and highly costly (35%-50% increase in cost) <br />Project descriptions specifies anchoring into fractured shale <br />
    16. 16. Locating Ideal Placement <br />Fractures in Shale are of interest to the oil and gas industry<br />Vertical Drilling is commonly used but many bore holes maybe required <br />Horizontal drilling is a relatively new method and it can cover a larger area <br />Horizontal drilling is more expensive<br />Drilling and closing the bore hole maybe difficult and time consuming <br />
    17. 17. Locating Ideal Placement <br />Fracture zones compared to host rock have:<br />Lower resistivity (higher conductivity)<br />Lower seismic velocity <br />Cause scattering of seismic and Ground Penetrating Radar (GPR) waves<br />Topographic depressions due to fracturing and weathering<br />
    18. 18. Placement of Concrete Slap Over Shale <br />Ends of the main cables need to be hooked into the concrete slab which will carry all of the loading from the bridge <br />Need to ensure shale is consolidated under the concrete slab <br />Concrete slap cannot be placed parallel to the shale bedding<br />Concrete slab cannot be placed parallel to the dipping angle of shale <br />Rock bolts and tendons used to keep shale intact<br />
    19. 19. Placement of Concrete Slap Over Shale <br />Post-tensioned Concrete will be used <br />Concrete slab will withstand the tension from the cables and the compressive loads from the weight of the anchor <br />Expansion and contraction from underlying rock are supported by the concrete without significant flexure<br />
    20. 20. Anchors of the Golden Gate<br />The Golden Gate is also anchored into shale using a concrete slab <br />Over one million tons of concrete was used to build the anchors that hold the cables in place<br />
    21. 21. Scour is one of the top three causes of bridge failure.<br />Approximately 60% of bridge failures are caused by scour at the abutments and the piers.<br />
    22. 22. Problems with Fractured Shale<br />
    23. 23. Bridge Maintenance <br />Initial Inspection<br />Intermin Inspection<br />Damage (Emergency) Inspections<br />Underwater Bridge Inspection<br />Fracture Critical Inspection<br />
    24. 24. Bridge Maintenance <br />

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