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Jet grouting method has been widely used in Taipei MRT
construction projects.
Busy traffic above improvement zone Drainage culvert above improvement zone Utility networks above improvement zone
limitation of construction space
complicated utilities layout at the shallow depth close to the existing underground facilities
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RJG named as Rapid Jet Gruting. Similar to the commonly used JSG method,
the RJG method uses a double-tube grouting system with two nozzles on the
opposite side of the monitor. The latter also uses air and jet stream to cut
and mix the in-situ soil with grout.
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Method Item
Jet Special Grout
(JSG method) Column Jet Grout(CJG method) Rodin Jet Pile(RJP method) Rapid Jet grout(RJG method)Effective diameter 1.0~2.0 m 1.2~2.0 m 2.0~3.0 m 2.5~4.5 mGeological condition
Sand SPT-N 50 SPT-N 200 SPT-N 100 SPT-N 100
Clay SPT-N 4 SPT-N 9 SPT-N 5 SPT-N 5
Design strength Sand 2~3 MPa 2~3 MPa 2~3 MPa 2~3 MPaClay 0.3~1 MPa 0.3~1 MPa 0.3~1 MPa 0.3~1 MPa
Drill hole diameter 0.12~0.15 m 0.14~0.25 m 0.14~0.25 m 0.14~0.25 m
Drill rod diameter0.06 m
(double-tube)
0.06 m or 0.09 m
(triple-tube)
0.09 m
(triple-tube)
0.06 m or 0.09 m
(double-tube)
Number of nozzles use 1 2 2 2
Jet grouting
material Binder Water Water Binder
total pressure 18~22 MPa 35~40 MPa 20 MPa 33~37 MPa
total flow rate 60 L/min 70 L/min 50 L/min 180 or 360 L/minTotal air pressure 0.6~0.7 MPa 0.6~0.7 MPa 0.76~1.05 MPa 0.7~1.05 MPa
Bindertotal pressure 2~5 MPa 40 MPa
total flow rate
140~180 L/min 190 L/min
Rod rotation
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0 8 16 24
SPT-N Value
0 25 50 75 100
Grain Size Distribution (%)
0
5
10
15
20
25
30
Depth(m)
< 0.075 mm
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The photo of grout column D excavated Measured diameter in silty sand layer Measured diameter in silty clay layer
Measured dimensionGrout column
1-1' section 2-2' section Design diameter
A Silty sand layer 3.7 m 3.1 m 2.0 mSilty clay layer 3.1 m 2.6 m
B Silty sand layer 3.4 m 3.6 m 2.5 mSilty clay layer 3.2 m 2.7 m
C Silty sand layer 3.6 m 3.8 m 3.0 mSilty clay layer 3.6 m 3.8 m
D Silty sand layer 4.6 m 4.7 m 3.5 mSilty clay layer 4.1 m 4.1 m
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Silty sand layer Silty clay layer
The evaluation grade of core sampl ing (from Takashi, 2003)
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0
1
2
3
4
5
6
7
Com
pressivestrength(MP
a)
Grout Column A Grout Column B Grout Column C Grout Column D
S 1
S 1
S 1
S 2
S 2
S 2
S 2
avg.
avg.
avg. avg.
S 3
(a) Silty Sand Layer
S 3
S 3S 3
Design strength
S 1
S 1 : Sample 1
S 2 : Sample 2
S 3 : Sample 3
avg. : Average
0
1
2
3
4
5
6
7
Com
pressivestrength(MP
a)
Grout Column A Grout Column B Grout Column C Grout Column D
S 1
S 1
S 3
S 1
S 3
S 1
S 3
S 2
S 2
avg.
avg.
avg.
avg.
S 3
(b) Silty Clay Layer
Design strength
S 2S 2
S 1 : Sample 1
S 2 : Sample 2S 3 : Sample 3
avg. : Average
There is no clear dif ference between the strengths of grout columns in silty
sand and in silty clay layers. It is mainly resulted by the not significant
different in fine content between silty sand and silty clay. The fine content
for silty sand is about 50% while the fine content of silty clay is about 80%.
To increase the strength of grout column in the silty sand layer, it needs toreduce the water/cement ratio in grout.
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1. RJG method can install grout columns with the diameter ranging from
3.1 to 4.6 m at the depth from 14 to 20 m in silty sand layer and silty
clay layer. The former has fine content of 48%; the latter has the SPT-N
value ranging from 5 to 10.
2. The fine content of the in-situ soil has a significant influence on the
unconfined compressive strength of RJG grout column. For example,
when the fine content of the grout column located in the silty sand
layer is as high as 48%, the unconfined compressive strength is almost
different from the grout column located in silty clay layer (fine content= 80%). To increase the strength of grout columns in silty sand layers,
the water-cement ratio of grout needs to be reduced.
3. Due to the large diameter of RJG grout column, the number of inclined
jet grouting piles can be minimized and the quality of overlapping grout
columns can be improved when grouting is carried out in complicated
subsoil condition or limited space.
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