Investigation of Consolidation Promoting Effect by Field and Model Test for Vacuum Consolidation Met

1
Investigation of Consolidation Promoting Effect
by Field and Model Test for Vacuum Consolidation
Method
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Background of research
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Purpose of research

• Prediction of behavior of the ground remains
  empirical
• Effect of vacuum-filling combined consolidation
  method hasnt been clarified

4
Field investigation
Outline of field investigation

• Construction period
• 20 November. 2003
• Improved area
• About 3300m2
• Improved depth
• About 12m
• Loading vacuum pressure
• About -68kPa

Construction spot panorama
5
Setting positions of instruments
No.164
Center of improved area
water-level observation well ground
inclinometer differential settlement gauge
pore water piezometer
End of improved area
Crack control hole
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Construction situation
Situation of countermeasure for peripheral ground
Situation of operation of vacuum pump
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Crack control hole
End of improved area
Improved area
6m
2m
15cm in diameter
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Relief well
End of improved area
30cm
Improved area
6m
Sand layer
2m
15cm in diameter
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Settlement
Vacuum pump operating all the day
S-3(GL-13.0m)
layer?
Settlement (cm)
layer?
ground surface
Installation depth of differential settlement
gauge
Time (day)
10
Groundwater level
W-1(Inside of improved area GL-13.0m)
The water is supplied into relief well
Vacuum pump operating all the day
W-2(Outside of improved area GL-6.0m)
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Summary of field investigation
Countermeasure for peripheral ground
Installation of relief well as countermeasure for
peripheral ground
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Model test
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Outline of sample
Result of laboratory soil testing left 2m from
sample
Result of laboratory soil testing left 2m from
sample
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Vacuum pressure transmitting rate (Upper layer)
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Vacuum pressure transmitting rate (Lower layer)
Vacuum pressure transmitting rate ()
Model(2003)
Field(GL-8.5m)
Model(2004)
Time (day)
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Stage loading test
Purpose
Simulation of rapid fill on soft ground when
vacuum-filling combined consolidation method used
Outline of stage loading test
Vacuum pressure of 68kPa is acted on specimen
Vacuum pressure of 68kPa is acted on specimen
Stage load of 17.7kPa(Height of filling of 1.0m)
is added
Failure
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Test result (GL-7.0mGL-7.9m)
Vacuum pressure transmitting rate
Volumetric strain
Load
Axial strain
Vacuum pressure
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Summary of model test
Prediction of behavior of the ground
Vacuum pressure transmitting rate of 2004 accords
with field investigation well
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Conclusion

• Pore water pressure of the ground could be
  forecasted by model test
• Fill of 10m or more is allowable on the ground
  when vacuum-filling combined consolidation method
  used

• Pore water pressure of the ground could be
  forecasted by model test
• Fill of 10m or more is allowable on the ground
  when vacuum-filling combined consolidation method
  used

• A effective countermeasure for peripheral ground
  was specified
• Influence depth of vacuum consolidation could be
  estimate

• A effective countermeasure for peripheral ground
  was specified
• Influence depth of vacuum consolidation could be
  estimate

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Vacuum consolidation method
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Pore water pressure
Crack control hole
1.8m
Setting position of pore water piezometer