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City of Winnipeg
SOUTHWESTERN RAPID TRANSIT CORRIDOR
Bidder Meeting
October 16th, 2009
Site Location
Field Investigations
- Klohn Krippen (2003) - Geotechnical• 4 deep test holes, 1 shallow• Groundwater monitoring• Laboratory testing
– AECOM (2009) - Geotechnical• 2 deep test holes ( rock coring)• Groundwater monitoring• Laboratory testing
– AECOM (2009) – Hydrogeological• Two test wells drilling• Field pump tests
Location of Test Holes
TW 2
TW 1
Soil Stratigraphy
Field and Lab Results
Groundwater Conditions–Clay : 2 m below ground, Elv. 231 m–Bedrock/Till : Elv. 224 to 226 m
–Impact on:• Excavation stability• Global stability• Seepage
Geotechnical Concerns
– Foundation type– Rebound, heave and settlement– Retaining walls– Base heave – Temporary shoring and excavation plan
Bearing capacity and foundation type
– Raft foundation – Design based on the concept of floating foundation– Bearing capacity and settlement pressure are defined
Rebound, Heave and Settlement
BRT - Heave Estimates for Excavations
223
224
225
226
227
228
229
230
231
0 25 50 75 100 125 150 175 200 225 250
Heave, mm
Excavati
on
Ele
vati
on
, m
elastic rebound
elastic rebound + sw ell @ 6 months
elastic rebound + sw ell @ 12 months
elastic rebound + ult sw ell
Retaining walls
- Reinforced Concrete U-shaped section - Reinforced Concrete Cantilever wall- Coulomb Theory- Design for surcharge from compaction during construction- Design for live load surcharge from Cooper E90 loading-
Clay
Till/Bedrock
FS = Wclay /γw h
Base heave
hWclay
FS against Base Heave
1.00
1.50
2.00
2.50
3.00
222.5 223.0 223.5 224.0 224.5 225.0 225.5 226.0 226.5
GWL in Bedrock Aquifer
FS
Excv 225.0
Excv 224.0
Excv 223.0
TYPICAL
EXTREME HISTORICAL
Temporary shoring and Excavation plan
– Cut and cover construction– Staged construction, Stage I and II– Site constrains:
• Limited space• Utilities• Private property• Proximity to CN tracks
– Excavations plan include:• Open excavation• Cantilever / Braced Shoring• Combination of shoring and open excavation
Temporary shoring and Excavation plan
– Excavation configurations• Open Excavation, up to 6 m cut• Other geometry < 6m cut
3
1
14
3
33
Temporary shoring and Excavation plan
– Excavation configurations• Braced Shoring up to 9.5 m
~ 9.5
4.6 Min
~ 5
Temporary shoring and Excavation plan
– Excavation configurations• Combination of Braced Shoring and Open excavation
4.6
3 - 5
2-3
1 37m bench
5 m Crane pad
varies 5 m Min.
varies 7 Max.
Temporary shoring and Excavation plan Lateral Loads from Surcharge
Temporary shoring and Excavation plan
Base Instability : analogous to bearing capacity
Global Stability
- Stress – stability coupled finite element analysis- Locally acceptable soil parameters- Account for excavation unloading - Model train loading- Design objective FS = 1.30
Stability output
Stability output
Stability output
Stress-Deformation Analysis
Stress-Deformation Analysis
Performance Monitoring Program
Instrumentation will be installed to monitor
– Displacement of railway tracks – Displacement of shoring system– Horizontal subsoil displacement– Excavation heave– Groundwater levels
THANK YOU