02 boscardin ppt fundaciones especiales
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fundaciones especialesTRANSCRIPT
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Conditions Where Diaphragm Walls Are Used
Marco D. Boscardin, PhD, PE, DGE
Boscardin Consulting Engineers, Inc.
DFI Seminar - 16 October 2012
What Drives Basement Construction Practices? Economy
Local Experience and Expertise
Local Tradition
Local Geology
Groundwater
Right-of-Way Issues
Other Site Constraints
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Why Use Diaphragm Walls?
Improved Control Ground Loss During Wall Construction
Improved Control Adjacent Ground Movements During Mass Excavation and Load Transfer
Control Groundwater Infiltration
To Serve as Final Walls and Load Bearing Elements
Alternatives such as T-Panels and Post Tensioning
Concrete Diaphragm Walls
Advantages Temporary and Perm. Groundwater Control
Less Vibration and Better Movement Control
Flexibility in Construction Sequence and Ground Conditions Accommodated
Limitations Work Area Needed
Cost
Specialized Equipment
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Where Diaphragm Walls are Used
When Large, Deep Basements are Needed
BCEICourtesy Nicholson and
Architect of The Capitol
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BCEI
Courtesy Nicholson and Architect of The Capitol
Where Diaphragm Walls are Used
When Large, Deep Basements are Needed
Dense Urban Settings Where Impact on Adjacent Properties a Concern
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Where Diaphragm Walls are Used
When Large, Deep Basements are Needed
Dense Urban Settings Where Impact on Adjacent Properties a Concern
To Eliminate the Need for Underpinning Existing Structures
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10 St. James
Braced Cut for Building
Where Diaphragm Walls are Used
When Large, Deep Basements are Needed
Dense Urban Settings Where Impact on Adjacent Properties a Concern
To Eliminate the Need for Underpinning Existing Structures
To Expedite Construction Schedule Serve as Final Walls Top-Down Construction Serve as Foundation Elements
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Russia Wharf Project
Where Diaphragm Walls are Used
When Large, Deep Basements are Needed
Dense Urban Settings Where Impact on Adjacent Properties a Concern
To Eliminate the Need for Underpinning Existing Structures
To Expedite Construction Schedule Serve as Final Walls Top-Down Construction Serve as Foundation Elements
Special Cases
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Circular Diaphragm Wall
Soft eye –Fiberglass piles
Diaphragm Wall for Tunnel Eye
North Shore Connector, Pittsburgh - AECOM
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T-Panels and Post-Tensioned Panels
Geotechnical Conditions and Diaphragm Walls
Compatible with Most Soil Conditions (Mechanical and Hydraulic Clam Rigs) Loose to Dense Sands
Soft to Stiff Clays
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Herbert Hoover Dike Rehabilitation
Hydraulic clamshell – Soilmec SM-870 with BH12 21
Herbert Hoover Dike Rehabilitation
Mechanical Clamshell
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Geotechnical Conditions and Diaphragm Walls
Compatible with Most Soil Conditions (Mechanical and Hydraulic Clam Rigs) Loose to Dense Sands
Soft to Stiff Clays
Compatible with Weaker Rocks (Hydromill) Hard Clay, Chalk, Shale, Sandstone
Hydromill Rig
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Herbert Hoover Dike Rehabilitation
Hydromill Cutter
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Cutter Soil Mixing (CSM) Rig
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Geotechnical Conditions and Diaphragm Walls
Compatible with Most Soil Conditions (Mechanical and Hydraulic Clam Rigs) Loose to Dense Sands
Soft to Stiff Clays
Compatible with Weaker Rocks (Hydromill) Hard Clay, Chalk, Shale, Sandstone
Difficulties with Soils Containing Many Boulders
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Drop Chisel for Rock Excavation
Vibrations and Wall Construction
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Geotechnical Conditions and Diaphragm Walls
Compatible with Most Soil Conditions (Mechanical and Hydraulic Clam Rigs) Loose to Dense Sands Soft to Stiff Clays
Compatible with Weaker Rocks (Hydromill) Hard Clay, Chalk, Shale, Sandstone
Difficulties with Soils Containing Many Boulders
Difficulties where Slurry is Lost – e.g. Karst, Coarse Gravels
Typical Goals for a Diaphragm Wall
Use Slurry to Counterbalance Lateral Ground and Water Pressures and Provide Support to Limit Ground Loss During Wall Excavation and Placement
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BCEI
Courtesy Nicholson
Typical Goals for a Diaphragm Wall
Use Slurry to Counterbalance Lateral Ground and Water Pressures and Provide Support to Limit Ground Loss During Wall Excavation and Placement
Place a Stiff Element in the Ground so that a Wider Support Spacing and a More Open Work Space are Possible
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Typical Goals for a Diaphragm Wall
Use Slurry to Counterbalance Lateral Ground and Water Pressures and Provide Support to Limit Ground Loss During Wall Excavation and Placement
Place a Stiff Element in the Ground so that a Wider Support Spacing and a More Open Work Space are Possible
Limit Water Inflows
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Russia Wharf Project
Diaphragm Walls and Water
Better than Other Conventional Walls Soldier Piles and Lagging Driven Sheet Piles
But Not Perfect, Shrinkage, Movement
Each Joint is a Potential Source of Leakage
Walls Flex and Joints Open and Close with Excavation and Filling
Can be Addressed with Special Joint Details
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LD-IV-1-10-39
Slurry Walls Not Totally “Watertight”
Soil Between Walls Excavated and “Dry” Side Exposed to Changes in Temperature and Humidity
P = Primary SPTC Wall Panel
S = Secondary SPTC Wall Panel
Gaps Grows Larger Between Concrete and Steel Pile on Dry Side Due to Shrinkage of Concrete as it Dries and is Subjected to Large Temperature Fluctuations
Surface Cracking Develops in Response to Cyclic Drying and Cyclic Freeze-Thaw
Example of an Improved Joint
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Diaphragm Wall Considerations
Panel Size Affects Ground Loss Affects Cost of Construction
Number and Types of Joints Affects “Water Tightness” Affects Load Transfer Between Panels
Support Spacing and Subgrade Soil Strength Overall System Stiffness Controls Ground Movements and Impacts on
Adjacent Structures
Opencut Movements
BCEIClough & O’Rourke, 1990
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Horizontal Wall Movement vs. Stiffness
BCEIClough & O’Rourke, 1990
Adaptable to Special Construction
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Jacked Tunnel Access Pits
Schematic Section of Jacking Pit Looking East
Cross Lot Bracing
Relief Holes
Frozen Soil
Post TensionSlurryWalls
Jet Grout In Situ Bracing
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Moveable Diaphragm Wall
Relief Holes Along Post-Tensioned Panels
Control of ground freeze pressures unique application in U.S.
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Summary
Diaphragm Walls a Competitive Alternative
Provides Enhanced Ground Loss Control During Wall Construction
Provides a Stiffer Support System to Better Control Ground Movements
Provides Improved Ground Water Control
Can Serve as Load Bearing Elements
Can be Reconfigured and Post-Tensioned for Greater Stiffness.