Our Tour Stops. A Foundation Engineering gtrip down the Mississippi River. Dan Brown, P.E. Dan Brown and Associates 9/6/2010.

Transcription

1 A Foundation Engineering gtrip down the Mississippi River Dan Brown, P.E. Dan Brown and Associates Our Tour Stops I 35W Minneapolis US U.S. 61 Bridge, Hastings, MN New Mississippi River Bridge (I 70), St. Louis John James Audubon Bridge, St. Francisville, La. Huey P. Long Bridge, New Orleans Map by Google 1

2 MN I 35W Replacement Emergency Design Build Contract $200,000/day bonus/penalty Testing important to: Testing Plan Verify required embedment into sandstone Demonstrate reliability of installation But timing was critical Allowed contractor to test prototype shaft 2

3 Early Issue Artesian Groundwater Test Shaft % Rec RQD Compr Str, tsf E le v., ft Compr Str (tsf), or RQD or Rec (%) 3

4 Top portion of rock extremely weathered & soil like, easy to drill with earth auger Socket defined from good rock as indicated by drilling resistance with rock auger Key Issues 35W Side Resistance avg 4

5 35W Side Resistance fsn q C u p a p a Elev , C 2.5 to W Base Resistance With 78 dia, ρ/b 0.01 at ρ= ksf/in For rigid circular footing on elastic half space: With ν = ¼ : E = 7,800ksf =54 ksi E 100q u for q u 550psi 2 qb 1 s 0.79 E 5

6 U.S. 61 Bridge over Mississippi River Hastings, Minnesota First Bridge (the Spiral Bridge Existing Bridge New Arch Bridge (under construction) Subsurface Profile at Bridge Shallow Foundations on Rock 42 Driven Pipe Pile Foundations to Rock 6

7 Bridge Foundations North Embankment Interbedded layers of Sand & Compressible Clay Sand Compressible Clay Compressible Clay Sand Sand Sand 7

8 Column Supported Embankment Plan Welcome to St. Louis! MoDOT graphic 8

9 New Mississippi Bridge, St. Louis Alternate Technical Concept (ATC) Prequalified Contractors only Pre bid confidential submittal of ATC for owner evaluation & approval Contractor may bid base design and/or preapproved ATC design DBA worked for Massman Traylor Alberici to develop ATC foundation design 9

10 Alternate Design Limestone Bedrock Compressive Strength Data Elevation (ft) ft Socket Post-Award 290 Pre-Award Post-Award Mean Pre-Award Mean ,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 Unconfined Compressive Strength (psi) Elevation (ft) Post-Award Pre-Award 16.5ft Socket Post-Award Mean (below elev 300) Pre-Award Mean ,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 Unconfined Compressive Strength (psi) Pier 11 Pier 12 10

11 Load Test Shaft Construction Load Test Shaft Construction 11

12 Load Test Shaft Construction Four O cells crammed tight New World Record test load: 73,000 kips! Over 40ksf avg mobilized unit side resistance 450ksf base resistance mobilized at < ¼ inch displ 2,000 ksf/in 2 qb 1 s 0.79 E For rigid circular footing on elastic half space with ν = ¼ : E = 191,000ksf = 1330ksi E 100q u for q u 13ksi 12

13 Audubon Bridge Cable stayed bridge, 1583 main span Two pylons: 3 x 7 group of 7.5 dia. Shafts High approach: 2 column piers Soil Conditions at Pylons SPT "N" (blows/ft) Silty Sands 0-50 Elevation (ft) Sand Sand with Layers of Sandy G l ShftTi Shaft Tip Elevation Clay Soils Undrained Shear Strength (tsf)

14 Base Grouting Enhance Axial Resistance Improve Reliability Mitigate Imperfections in Base Conditions Criteria: Target Pressure Minimum Net Volume Limit Upward Shaft Movement Base Grouting Tube á Manchette (using CSL tubes) Cover Plate 14

15 Casing & Oscillator System Excavation 15

16 Dan Brown & Associates 16

17 Base Grouting Measurements Pressure (Auto) Pressure (Manual) Volume Grout Pressure (psi) Net Net Net Grout Volume (cu. ft.) Net Time (minutes) 0 17

18 Performance During Grouting O cell Load Testing w/ Reaction Frame 18

19 0.00 Load Test Results O-Cell Load (tons) ,000 1,500 2,000 2,500 3,000 3,500 Base Grouted rd Displacement (inches). Downwar NOT Base Grouted 136ksf (950psi) 5.00 Shaft 11W Load Test Shaft T2 Load Test Shaft T4 Load Test Shaft 11E Load Test Shaft 15E Load Test Shaft T3 Load Test Two Odd Shafts O-cell load (MN) Displacement (inches) Not Grouted 1W Construction Difficulty 4W CISS 0 1,000 2,000 3,000 O-cell load (tons) Displacement (mm) 19

20 Huey P. Long Bridge Widening Owner: La. DOTD Structural Engineers: Modjeski and Masters Geotechnical Engineers: Eustis Engineering General Contractor: Kiewit/Massman/Traylor Subcontractor: Malcolm Drilling Company Foundation Consultant: Dan Brown and Associates Pier IVA Test Shaft Production Shafts 20

21 Rotator System 21

22 Casing Excavation Using Hammer grab 44 22

23 Shaft Cleaning & Inspection Airlift SID Bottle Brush (Hydraulic) Cleaning Bucket Place Gravel 45 Reinforcement Bar Splices Backbone Frame 23

24 Placement of Reinforcement Shaft/Cap Connection Isolation Casing Shaft Cutoff at 11 24

25 Concrete Recover (7 oz/cwt) VMA (3 oz/cwt) 49 Base Grouting 25

26 Base Grouting QC/QA 51 Performance of Load Test 1.0 0, inches Displacement, , inches Displacement, ksf Load, kips Load, kips 26

27 Completed Foundation Summary Foundations for large bridges present special challenges: key issues Construction plan to minimize risks Constructability issues of design Coordinated effort of partners Performance verification i requirements Don t get bit! 27