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Investigation of Consolidation Promoting Effect by Field and Model Test for Vacuum Consolidation Method Nagasaki University H.MiharaY.TanabasiY.JiangT.Shiono.

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Presentation on theme: "Investigation of Consolidation Promoting Effect by Field and Model Test for Vacuum Consolidation Method Nagasaki University H.MiharaY.TanabasiY.JiangT.Shiono."— Presentation transcript:

1 Investigation of Consolidation Promoting Effect by Field and Model Test for Vacuum Consolidation Method Nagasaki University H.MiharaY.TanabasiY.JiangT.Shiono Maruyama Industry Co,Ltd

2 Background of research soft ground Reinforcement Pre-loading method Pre-loading method Deep mixing stabilization method Vacuum consolidation method Behavior prediction and site management remain empirical Influence on peripheral ground is large Social demand Social demand Less cost Less cost Less constructing period Improvement of vacuum consolidation technology Construction cases using vacuum consolidation method are increasing Vacuum consolidation method

3  Prediction of behavior of the ground remains empirical  Effect of vacuum-filling combined consolidation method hasn’t been clarified Purpose of research Investigation of consolidation promoting effect of vacuum consolidation method  Countermeasure for peripheral ground hasn’t been specified  Influence range of vacuum consolidation remains uncertain Field investigation  Countermeasure for peripheral ground hasn’t been specified  Influence range of vacuum consolidation remains uncertain  Behavior prediction of the ground remains empirical  Effect of vacuum-filling combined consolidation method hasn’t been clarified Model test  Behavior prediction of the ground remains empirical  Effect of vacuum-filling combined consolidation method hasn’t been clarified

4 Field investigation Construction spot panorama Outline of field investigation  Construction period 20 November ~ 20 November ~  Improved area About 3300m 2 About 3300m 2  Improved depth About 12m About 12m  Loading vacuum pressure About -68kPa About -68kPa 17.6m 187m th construction field

5 Setting positions of instruments No.164 End of improved area 8.8m 8.0m Center of improved area W-1 GL ‐ 13.00m water-level observation well ground inclinometer differential settlement gauge pore water piezometer Crack control hole 2.4m 3.8m 2.0m P-3-1 GL ‐ 3.50mP-3-2 GL ‐ 8.50m P-2-1 GL ‐ 3.50mP-2-2 GL ‐ 8.50m ‐ 8.50m P-1-3 ‐ 5.20m P-1-2 GL ‐ 3.50m P-1-1 ‐ 13.00m S-3 ‐ 11.30m S-2 GL ‐ 5.10m S-1 GL ‐ 6.00m W-2 road water-level observation well W-1 GL ‐ 13.00m GL ‐ 6.00m W-2 ground inclinometer differential settlement gauge GL ‐ 5.10m S-1 ‐ 11.30m S-2 ‐ 13.00m S-3 pore water piezometer GL ‐ 3.50m P-1-1 ‐ 5.20m P-1-2 ‐ 8.50m P-1-3 P-2-2 GL ‐ 8.50mP-2-1 GL ‐ 3.50m P-3-2 GL ‐ 8.50m P-3-1 GL ‐ 3.50m Crack control hole 2.0m

6 Construction situation Situation of countermeasure for peripheral ground Situation of operation of vacuum pump Before vacuum pump operating Installation of crack control hole To pre-estimate the influence on peripheral ground 20 November ~ 26 December Vacuum pump operating for 9 hours a day 7 December Installation of relief well To reduce the influence on peripheral ground 5 January ~ Vacuum pump operating for all the day

7 Crack control hole End of improved area 6m 15cm in diameter 2m30cm Sand layer To place crack control hole for monitoring Improved area 6m 15cm in diameter 30cm2m

8 Relief well End of improved area Improved area 30cm 6m 15cm in diameter 2m Sand layer Supply of the water To prevent seepage from peripheral ground Water level observation well W-2

9 Settlement Settlement Settlement (cm) Time (day) Vacuum pump operating all the day layer ① layer ② ground surface S-3(GL-13.0m) ① ② 5.1m -5.1m S m -11.3m S m S-3 Installation depth of differential settlement gauge

10 Groundwater level Measuring day (date) Water pressure (kPa) The water is supplied into relief well Vacuum pump operating all the day W-2(Outside of improved area GL-6.0m) W-1(Inside of improved area GL-13.0m)

11 Influence range of vacuum consolidation There was no reaction both differential settlement gauge S-3 and water level observation well W-1 Summary of field investigation Countermeasure for peripheral ground Installation of relief well as countermeasure for peripheral ground Deformation on peripheral ground is reduced Installation of relief well as countermeasure for peripheral ground There is no effect of vacuum consolidation under improved depth There was no reaction both differential settlement gauge S-3 and water level observation well W-1

12 Loading device Displacement gauge Load cell Triaxial chamber General drawing of Experimental apparatus Operation panel Triaxial chamber Pore water gauge Specimen Drain Triaxial chamber Vacuum pressure –68kPa –68kPa Vacuum pressure –68kPa –68kPa Model test Water Lateral pressure Axial force

13 Upper layer Lower layer Outline of sample depth ( GL - m ) specimen No. water content W n ( % ) porosity e 0 degree of saturation S r (%) unconfined compressive strength q u (kN/m 2 ) 2.00 ~ 2.90 T ~ 3.90 T ~ 4.90 not adopted ~ 6.90 T ~ 7.90 T ~ 8.90 T ~ 9.90 T ~ not adopted ~ not adopted ㎝ 15cm Specimen Result of laboratory soil testing left 2m from sample

14 Vacuum pressure transmitting rate Pore water pressure Vacuum pressure ×100(%) Time (day) Vacuum pressure transmitting rate (%) Field(GL-3.5m) Model(2003) Model(2004) Vacuum pressure transmitting rate (Upper layer) Vacuum pressure transmitting rate (Upper layer) 40%

15 Vacuum pressure transmitting rate (Lower layer) Vacuum pressure transmitting rate (Lower layer) Time (day) Vacuum pressure transmitting rate (%) Model(2003) Model(2004) Field(GL-8.5m) 40%

16 Outline of stage loading test Vacuum pressure of –68kPa is acted on specimen Stage load of 17.7kPa(Height of filling of 1.0m) is added Failure Stage loading test Purpose Simulation of rapid fill on soft ground when vacuum-filling combined consolidation method used To estimate the limit height of filling Simulation of rapid fill on soft ground when vacuum-filling combined consolidation method used Vacuum pressure of –68kPa is acted on specimen Stage load of 17.7kPa(Height of filling of 1.0m) is added Vacuum pressure transmitting rate reaches 60% Stage load is added when vacuum pressure transmitting rate reaches 60% again Failure

17 Test result (GL-7.0m ~ GL-7.9m) Time (min) Vacuum pressure Axial strain Volumetric strain Load Vacuum pressure transmitting rate 177kPa 4180min 4630min 460.1kPa Failure

18 Effect of vacuum-filling combined consolidation method Limit filling load is circumscribed within range of 177kPa ~ 460.1kPa Vacuum pressure transmitting rate of 2004 accords with field investigation well Prediction of behavior of the ground Summary of model test Pore water pressure of the ground can be forecasted by model test Vacuum pressure transmitting rate of 2004 accords with field investigation well Fill of 10m or more is allowable on the ground since load of 177kPa is equivalent to pressure of 10m filling high Limit filling load is circumscribed within range of 177kPa ~ 460.1kPa

19 Field investigation  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 Conclusion Model test  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 Consolidation promoting effect of vacuum consolidation method could be clarified partially

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21 Horizontal drain Vertical drain Airtight sheet Perforated drainage pipe Vacuum pump Vacuum consolidation method Flow of drainage Direction of force

22 Pore water pressure (kPa) Measuring day (date) Vacuum pump operating all the day (1/5) Vacuum pump operating for 9 hours (11/20) Pore water pressure Setting position of pore water piezometer 1.8m 1.8m Improved area End of improved area Crack control hole GL-8.5m GL-3.5m


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