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1057824 Cheng PPT.pdf

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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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