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.
1. SR 532 Widening Project
Stillaguamish River Bridge
Replacement
Mike Harney, MS, PE
Oliver Hoopes, MS, EIT
Stan Boyle, PhD, PE
Shannon & Wilson
February 23, 2011
2. Outline
• Design-Build
• SR 532 Widening Project
• Stillaguamish River Bridge
– Subsurface Conditions
– Geotechnical Design
– Geotechnical Construction
• Summary
3. Traditional Design-Bid-Build
Identify
Owner
Project
Design
Plans and
Specifications
Team
Bid
Contractor Construct
11. DBT Concept Bridge – As-Built
Ground Improvement Bridge Piers
Retaining Walls Unreinforced Slopes
Reinforced Slopes
• Eliminated Walls
• Converted Walls to Less-Costly Slopes
• Eliminated Ground Improvement
• Removed Bridge Pier from the River
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?
24. Static Global Stability – No Stone Columns
FS < 1.5
N.G.
Upper sandy SILT
Fine SAND interbedded with SILT seams
Lower clayey SILT
Med. Dense to Dense Silty Fine SAND and Fine Sandy SILT
Med. Dense to Dense Sandy GRAVEL
Dense to Very Dense, Gravelly SAND
25. Post-Seismic Global Stability – No Stone Columns
FS << 1.1
N.G.!
Upper sandy SILT
Fine SAND interbedded with SILT seams
Lower clayey SILT
Med. Dense to Dense Silty Fine SAND and Fine Sandy SILT
Med. Dense to Dense Sandy GRAVEL
Dense to Very Dense, Gravelly SAND
26. Post-Seismic Global Stability – With Stone Columns
FS > 1.1
O.K.! Stone Columns in SILT
Upper SILT
Stone Columns in SAND
Fine SAND interbedded with SILT seams
Lower clayey SILT
Med. Dense to Dense Silty Fine SAND and Fine Sandy SILT
Med. Dense to Dense Sandy GRAVEL
Dense to Very Dense, Gravelly SAND
27. Static Global Stability – With Stone Columns
FS > 1.5
O.K.!
Stone Columns in SILT
Upper SILT
Stone Columns in SAND
Fine SAND interbedded with SILT seams
Lower clayey SILT
Med. Dense to Dense Silty Fine SAND and Fine Sandy SILT
Med. Dense to Dense Sandy GRAVEL
Dense to Very Dense, Gravelly SAND