Geotechnics for Sustainable Development - Geotec Hanoi 2013, Phung (edt). Construction Publisher. ISBN 978-604-82-0013-8

Performance of V-JET method for arrival of shield tunnellingmachineS. H. Cheng & H. J. Liao
National Taiwan University of Science and Technology, Taipei, Taiwan. E-mail: shcheng@mail.ntust.edu.tw

Ricky K. N. Wong & Iwakubo Takeshi
Sanshin Corporation Ltd., Taipei, Taiwan. E-mail: sanshin.tpe@msa.hinet.net

Y. H. Hsieh
Department of Rapid Transit Systems, Taipei, Taiwan. E-mail: yhshieh@trts.dorts.gov.tw

Keywords: shield tunneling, jet grout, watertight, strength.
ABSTRACT: This paper reports a case study of jet grouting project which involves constructing awatertight grouted zone under a drainage culvert as part of the arrival process for shield machine. To
minimize the number of grouting hole drilling in a congested street, the V-JET method which consisted ofa modified jet nozzle and an increased flow rate and jet grouting pressure was adopted for this project.
Among the 38 grouting holes of 20 m deep drilled in this project, 10 were drilled through the culvert. All
grout piles are expected to have a nominal diameter of 3.5 m, which was verified later with sounddetectors during jet grouting. The strength of grouted piles indicated can meet the design specifications(2.36 MPa for silty clay and 3.25 MPa for silty sand). The entire jet grouting project of 1750 m3 in cement
grout volume (W/C = 1.22) was finished in 105 days. It can assure the stabilization and waterproof of soil
around cutting face of arrival shield tunneling. The work of joint shield tunnel and the existing station
was successfully accomplished.
1. INTRODUCTION

the construction experience of Taipei MRT, jetgrouting method is widely applied for stabilization
and waterproof of soil around shield tunnelingmachine and underground stations. It also lowers
risks of negative effect on third parties. But in recent
years, as mentioned earlier, the limitation andcomplexity of underground space of other uses
involve multiple constraints and potential conflicts.
This increases more challenge to the design andconstruction of jet grouting method in the ground
improvement work.
This paper will report a case study of jet grouting
project, which involves the construction of a watertight grouted zone under a drainage culvert, for thearrival of shield machine of Tucheng extension line
(Yongning Station  Dingpu Station) in Taipei
MRT. To minimize the number of grouting holes
drilling in a congested street, the V-JET method was
adopted. This study will present the histories of jet
grouting carried out in the field and the measurestaken to ensure the quality of jet grout piles.

Causes of traffic congestion, difficulties of obtaining
construction sites, and other environmental factors
result in an intense demand for grate utilization ofunderground spaces in urban areas. Taking Taipei
MRT for example, more than 2/3 of construction was
built underground over the past two decades.
However, under the rapid development ofurbanization, there might be conflicts between the
progressing construction projects and their nearby
infrastructure’s foundation, drainage culvert, utility
networks or other underground facilities, which
increase construction difficulties and risks.
In the last decade, increasing demand forunderground space in urban areas has been goes forshield tunneling technological progress, especiallyground improvement measures such as grouting or
artificial ground freezing. It provides pre-supportingof soil in order to increase safety of construction
project, has been limit the need of costly and timeconsuming (Anagnostou and Rizos, 2009). Hence, in
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2. SITE CONDITIONS

properties of the sites, a thorough geologicalinvestigation was carried out at each ground
improvement site. The SPT-N values, grain size
distribution and physical soil properties profiles areshown in Figure 2. The subsoil condition near
Yongning Station (arrivel site of shield tunnel), thegroundwater level at site is 3.7 m below surface,
The upper 12.5 m of silty clay layer has somedrifted wood embedded. It has the undrained shear
strength (Su) about equal to 30 KPa. Between thedepth of 12.5m to 22 m, it is a silty sand layer(friction angle ' = 28o~30o) embedded with large
numbers of drifted wood. Below the depth of 22 m,
it is mostly loosely cemented weathering sandstone
and with the unconfined compressive strength (qu)equal to 5~20 MPa.

Tucheng extension line (Yongning Station 
Dingpu Station) of Taipei MRT is located in thesouthern part of Taipei Basin. The depth of shieldtunnel ranges from 9.58 m to19.82 m below groundsurface. Its subsoil condition varies from silty clay,
silty sand to weathering sandstone. Along theTucheng extension line, four sites are considered tohave high risk potential, namely the departure siteof shield machine (at Dingpu station), the arrival
site (at Yongning station) and two cross-passage
sites between shield tunnels (Figure 1). Double
packer (DP) grouting method and jet grouting
method are used to improve the mechanicalproperties and water tightness of soil near the highrisk sites. To better understand the subsoil
DP grouting for start ofshield tunnelling machine
DP grouting for protect ofcontact channel when excavation

DP grouting for protect ofcontact channel when excavation

Jet grouting for arrival ofshield tunnelling machine

Dingpu station(new build)

Yongning station(existed)

1,529 mFigure 1. The route and improvement zones of pre-construction condition of Tucheng extension line, Taipei MRT
Soil Classification

SPT-N Values

0
Backfill

25

50

75

Grain Size Distribution (%)

100

0

25

50

75

100

Water content, w (%) Unit weight, rt(t/m3)

0 20 40 60

0.0

1.5

3.0

Specify gravity, Gs

2.0

2.5

Void ratio, e

3.0 0.00 0.75 1.50

0
< 0.002mm << 0.075mm <

3
3.7 m

CL

6

Depth (m)

9

12

15
SM

18

21
SS

24

Figure 2. The SPT-N values, grain size distribution and soil properties profiles of arrival site (at Yongning Station)2

3. DESIGN AND GROUTING METHODS

3.2 Outlines of V-JET method

The zone to be grouted for the arrival of shieldtunneling machine is equal to 2,426 m3[approximate dimension of 24m (L) X 10m (W) X
10m (H)]. The arrival site is located under a busy
main street of Tucheng city and is near the
residential area, too. The traffic and noise problems
are two main concerns for this jet grouting project.
In addition, the zone to be grouted was in conflictwith the nearby utility network and the drainage
culvert (Figure 3). Due to the complexity of the
project, it is necessary to have a detailed study on
the construction methods in advance before
carrying out the grouting job to minimize the risk
involved. Evaluation on the design and grouting
methods taken before construction are illustrated asfollows:

Similar to the commonly used JSG method, the VJET method uses a double-tube grouting systemwith two nozzles on the opposite side of themonitor in different levels. The latter also uses air
and jet stream to cut and mix the in-situ soil withgrout. A larger nozzle diameter of 3~4.2 mm isused to allow a larger grouting rate. The grouting
parameters used here are as follows: grouting
pressure = 33~37 MPa, grouting rate = 180 or 360
or 540 l/min, and rod rotation and withdrawal rate
= 2~5 rpm and 10~18 min/m. Using theseparameters, the grouting capacity can be increased
to 35.3 m3/hr. So, it can rapidly install a grout pilewith a diameter up to 2.0~5.5 m at a depth up to 50
m below ground surface. More details of the V-JET
method and comparison with existing grout
methods are illustrated in Table 1.

3.1 Design evaluation
4. PERFORMANCE OF GROUTING WORK

Since there is a drainage culvert located between
ground surface and shield tunnels, trial layouts ofdrilling holes was adopted before jet grouting. Boththe inclined holes and vertical holes layouts wereused to study the optimum drilling plan and grout
pile diameter for this jet grouting job. As shown in
Figure 4(a), if the grout pile with the diameter
equal to 1.2 m is adopted and the drainage culvert
needs to be avoided, totally 345 grout holes in total.
It includes 161 inclined grout holes with dip angles
varying from 18o to 36o. Alternatively, Figure 4(b)shows the grout holes layout without inclined holes.
But it needs to drill 92 grout holes through thedrainage culvert. It is concerned that drilling somany holes through the drainage culvert may havea bad effect on the integrity and function of theculvert. Especially, it may result in a serious
leaking problem for the drainage culvert. So, thegrout holes layouts shown in Figures 4(a) and 4(b)was not adopted. Instead, the grout holes layout of
Figure 4(c) was used to reduce the numbers ofgrout holes to 38 and only 10 holes must be drilled
through the culvert. It certainly can maintain abetter function of the drainage culvert andconsequently minimize the risk involved in the jet
grout practice. To carry out the grouting job of
Figure 4(c), the designed diameter of grout pile
must be more than 3.5 m. So the jet nozzle of themonitor and the grouting parameters such as flow
rate, grouting pressure, and rod withdraw rate androtation rate are needed to be modified accordingly.

During construction, in order to proceed ground
improvement, it is required to prevent the nearby
soils from collapsing or water and sand gushing
while the closed shield machine was arriving
Yonging Station to pass through diaphragm wall inorder. Within limited space and under the conditionof obstacle of drainage culvert and utility networks,
V-JET method is applied in construction according
to design evaluation. After improvement, thecompressive strength of silty clay layer is set toincrease to 1.2 MPa, while that of the silty sandlayer is set to increase to 2.0 MPa and thepermeability of the improved zone is set to lessthan 1×10-5 cm/sec.
To avoid causing traffic problems on busy
roads, this grouting project was carried out inthree different stages: (1) Find out theunderground obstacles and remove them. Carryout the pilot grouting test. Complete 14 grout
piles on the southern side of the drainage culvert.
(2) Drill 10 grout holes through the culvert. Seale
the annular space between drill rod and boredhole on the upper and lower slab with water sealbox. Construct the grout piles beneath thedrainage culvert. (3) Complete 14 grout piles on
the northern side of the drainage culvert. The
details of the jet grouting work are shown in
Table 2 and Figure 5.As shown in Table 1, thenumbers of nozzle adopted for the V-JET
grouting were 2 and the flow rate was 360 l/min
compared to 1 nozzle and 60 l/min flow rate used
for traditional JSG method. Meanwhile, the rod
rotation rate was decreased to 2-5 rpm to allow3the grout jet to cut deeper into the soil. But theoverall grouting time was not slow down because
the rod withdraw rate was increased to 12 min/m
to compensate the slower rotation rate. Totally,
38 jet grout piles (diameter = 3.5 m, grouted
depth varied from 9.58 to 19.82 m below grout(a) Busy traffic above improvement zone

surface) were installed at the arrival site of shieldmachine. Grout material used in this jet grouting
project was slag cement with the water-cement
ratio equal to 1.22. Table 1 summarizes thegrouting parameters adopted in this project andthe comparison with existing grout methods.

(b) Drainage culvert above improvement zone (c) Utility networks above improvement zone

Figure 3. Pre-construction condition of arrival site of shield machine (nearby Yongning Station )13.38 m13.38 m13.38 m10.10 m10.10 m10.10 mDiaphragm Wall

Diaphragm Wall
Drainage
Culvert6.24 mDrainage
Culvert

2.0 m

2.0 m

6.24 mDrainage
CulvertDrainage
Culvert

1.0 m

1.0 m

1.0 m

10.88 m10.88 m10.88 m

2.0 m

2.0 m

6.24 m

2.0 m

2.0 m

6.24 m

2.0 m

2.0 m

6.24 m10.24 m10.24 mProfile Section

2.0 m

2.0 m

3.14 m3.14 m10.24 mDiaphragm Wall

Diaphragm Wall

Drainage
Culvert10.24 mProfile Section

Profile Section

Drainage Culvert

Drainage Culvert

10.10 m10.10 m10.10 m2.50 m10.24 m6.24
6.24 mm

2.50 m10.24 m10.24 m1.50 m10.24 m19.82 m19.82 m6.24 m2.50 m
6.24 m10.24 m1.50 m10.24 m10.24 m10.24 m10.24 m10.24 m10.24 m10.24 mDN Tunnel

UP Tunnel

DN Tunnel

UP Tunnel

DN Tunnel

UP Tunnel

Plan Section

2.0 m

10.24 mDrainage Culvert

19.82 m6.24 m3.14 m10.24 m1.50 m2.0 m

Diaphragm Wall

Diaphragm Wall

Drainage
CulvertPlan Section

Plan Section

Descriptions：

Descriptions：

Descriptions：

1. Design grout column diameter = 1.2 m
2. Total borehole numbers = 345
3. Inclined borehole numbers = 161(dip angle=18~36)

1. Design grout column diameter = 1.2 m
2. Total borehole numbers = 276
3. Numbers of drilling hole pass throughthe drainage culvert = 92

1. Design grout column diameter = 3.5 m
2. Total borehole numbers = 38
3. Numbers of drilling hole pass throughthe drainage culvert = 10(a) Jet grouting method(b) Jet grouting method(c) V- JET grouting method(inclined hole grouting)(drill through the drainage culvert)(drill through the drainage culvert)

Figure 4. Proposed jet grouting layouts for the arrival site

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Table 1. Comparison of different jet grouting methods (after Yong et al., 1996; Yoshida et al., 1996)
MethodItem
Effective diameter
Sand
Geologicalcondition
clay
Sand
Designstrength
Clay
Drill hole diameter

Jet Special Grout(JSG method)

Column Jet Grout(CJG method)Rodin Jet Pile
(RJP method)

V-JET method

 1.0 ~ 2.0 m
SPT-N  50
SPT-N  4
2 ~ 3 MPa
0.3 ~ 1 MPa
0.12 ~ 0.15 m
0.06 m 1.2 ~ 2.0 m
SPT-N  200
SPT-N  9
2 ~ 3 MPa
0.3 ~ 1 MPa
0.14 ~ 0.25 m
0.06 m or 0.09 m

 2.0 ~ 3.0 m
SPT-N  100
SPT-N  5
2 ~ 3 MPa
0.3 ~ 1 MPa
0.14 ~ 0.25 m
0.09 m 2.5 ~ 4.5 m
SPT-N  100
SPT-N  5
2 ~ 3 MPa
0.3 ~ 1 MPa
0.14 ~ 0.25 m
0.06 m or 0.09 m(double-tube)
1
Binder(triple-tube)
2
Water(triple-tube)
2
Water(double-tube)
2
Binder18 ~ 22 MPa
60 L / min
0.6 ~ 0.7 MPa

20 MPa50 L / min
0.7 ~ 1.05 MPa
40 MPa33 ~ 37 MPa
180 or 360 L / min
0.7 ~ 1.05 MPa－

35 ~ 40 MPa
70 L / min
0.6 ~ 0.7 MPa
2 ~ 5 MPa－

140 ~ 180 L / min

190 L / min－<10 rpm<6 rpm<6 rpm

2~5 rpm

16 ~ 40 min/ m
4.0 m3 / hr
0.9 m3 / m3
1.3 m3 / m3

16 ~ 25 min/ m
11.8 m3 / hr
0.9 m3 / m3
1.8 m3 / m3

15 ~ 20 min/ m
18.5 m3 / hr
0.6 m3 / m3
1.0 m3 / m3

8 ~ 16 min/ m
35.3 m3 / hr
0.5 m3 / m3
0.7 m3 / m3

Drill rod diameter
Number of nozzles use
material
Jet
total pressure
grouting
total flow rate
Total air pressure
total pressure
Bindertotal flowrate
Rod rotation
Withdrawal rate
Grouting capacity
Binder consumption
Amount of sludge－

Table 2. Details of jet grouting work at different stages
Work stage
1st stage

Work days*
38

Number of grout pile
14

Length of grout pile
10.24 mVolume improved
1140.85 m3

2nd stage

37

10

10.24 m144.69 m3

3rd stage
30
14
10.24 m1140.85m3* Work days include traffic re-routing, trial pit excavation, protection and restoration of utilities lines at eachstage.

Nearby buildings

Diaphragm Wall

3rd stage

Chung Yung Road

2nd stage

Drainage Culvert

1st stage

V-JET grouting equipment
Figure 5. Improvement zones and layout of grouting equipment at different stages

5

Sludge pit(a) water sealdrainage culvert

Waterproof grouted(b) Drill tube in the drainage culvert
Grouted pileLow pressure waterproof grouting※ material = slag cement + sodium silicate grout※ Flow rate = < 15 L/min※ Pressure = 0.8~1.0 MPa

The profile of grouting drill through the drainage culvert

Steel lap(c) seal box

Lock up of steel plate(d) seal the holes on the the upper and lower slab of the culvert

Figure 6. Photos of treatment condition during jet grouting under drainage culvert

4.1 Construction procedure

the holes on the upper and lower slab of the culvert
with no shrinkage cement and steel plate.

To maintain the function of drainage culvert during
and after the jet grouting practice, the construction
procedure taken for this grouting project is
illustrated in Figure 6: (1) Excavate the soil coverof the drainage culvert. Position the drill rig. Drill
the casing pipe (diameter = 300 mm) through theupper slab and stop at the lower slab; (2) Install thewater seal box outside the casing pipe to stop
groundwater flowing in from the bottom of theculvert. Replace the casing pipe with a double pipe
(diameter = 200 mm) with the monitor mounted at
the tip to continue drilling to the design depth; (3)Start jet grouting and withdraw the double pipe.
Let the slime overflow through the casing to thesurface. Jet grouting stops at some distance below
the bottom of the culvert. Withdraw the double
tube drilling rod; (4) Insert a 40 mm grout pipe toinject the slag cement + sodium silicate grout at an
injection rate of 15 l/min and grouting pressure of
0.8~1 MPa to strengthen the soil between the topof jet grout pile and the bottom of culvert; (5) Seal

Figure 7. Layout and results of sound detecting test
4.2 Effectiveness of grouting work
To verify the pile diameter constructed by the VJET method under various grouting parameters andin different soil conditions (silty clay layer andsilty sand layer), sound detectors were installed toconfirm the pile diameter before the first stage
construction was carried out. As Figure 7
demonstrates, the tube and sound detectors were6

installed at distances of 3.2m, 3.5m, and 3.8m fromthe grouting point respectively. In general, thedrilling alignment of the grouting hole wassatisfactory. There was less than 10 cm off thealignment over a drilling depth of 17 – 20 m. All
the sound detectors located at different locations
could pick up the sound of jet stream. It verified
the design pile diameter of 3.5 m, which had beenachieved successfully. Using the unconfinedcompressive strength and the falling head
permeability test after the completion of grouting(28 days), 2 grout piles were randomly chosenfrom 38 grout piles for the quality check. Coredsamples were taken from the piles and inspectedfollowing the evaluation method for high pressure
injection mixing piles proposed by the Japan
Society of Civil Engineers (Takashi et al., 2003).
The core samples are shown in Figure 8 and all are
rated acceptable. Besides, from the consolidated
undrained triaxial test run on cored samples, theeffective shear strength parameters are increased toc’= 50 ~ 70 KPa, ’= 50o ~ 63o for silty sand layer
and c’= 200 ~ 960 KPa, ’= 28o ~ 55o for silty clay
layer. Also, the compressive strength andpermeability of cored samples can meet the design
requirement (Figure 9).

4.3 Cutting work of arrival shield tunnel
While crossing the joint of Tucheng extension Lineand the operating Yongning station, the existing 80
cm thick diaphragm wall, 100 cm think headwall,
30 cm thick flood wall and acoustical wall at thestation are needed to be broken. To ensure safety of
cutting work at arrival of shield tunnel, the shieldmachines needs to stop work for check up, forcoordinates examination, and to be backfill
grouting when it approaches in front of arrival
shield tunnel (about 20 m before the diaphragmwall of the existing station). The cutting work
cannot continue until all conditions are foundworking normal. As shown in Figure 10 of the
cutting block within the improved area, its quality
is very similar to the core specimens of Figure 8,
which proves a very nice quality of constructionthat can assure stabilization and waterproof of soil
around cutting face of arrival shield tunnelling.
Backfill

0
Falling head permeability test 1
Falling head permeability test 2

3
6CL

Depth (m)9

Design value = 1X10-5
Design strength forsilty clay =1.2 MPa

Design strength forsilty sand =2.0 MPa

12
15

Improved zone

Improved zone

SM

18
21
SS

24

0.0

0.8

1.6

2.4

3.2

Compressive strength (MPa)

4.0

10-8

10-7

10-6

10-5

10-4

10-3

Coefficient of permeability (cm/sec)

Figure 9. Permeability and compressive strength ofgrout piles in silty clay/silty sand layer (cured 28 day)Cutting work does not influence Yongning
Station’s normal operation and trains safety. After
successful cutting of the existing diaphragm walland headwall at the station and after the shieldmachines are removed from operation platform, theshield machines are to be carried to the departureend (Figure 11a). The 1.65 m flood wall andacoustical wall can be broken by chain saw withlow vibration and low noise. Figure 11b presents
the drilling positions, quantity of cut block and thecut section of acoustical wall. Finally, the cutting
work of arrival shield tunnel takes three months toaccomplish.
5. CONCLUSIONS
Jet grouting was carried out as the ground
improvement work for the arrival of shield

Figure 8. Cored specimens from improved zone7

machine in Yongning Station of Taipei MRT.
Located in between ground surface and shieldtunnel, there was a drainage culvert in the way forthis grouting project. This paper reports theexperience learned from the practice of V-JET
grouting project under such a difficult condition.
The following conclusions were drawn from thefindings of this project:
1) By minimizing the number of grouting holes(either vertical or inclined one), V-JET method canfacilitate the grouting job in the congested area orunder the busy road. As a result, the quality of thegrout piles and the overlapping portion between
neighboring piles can be improved.

2) The drainage culvert located between groundsurface and shield tunnels was the obstacles ofthis grouting project. 10 grout holes must drill
through the drainage culvert. By proper
arrangement of casing drilling, groundwatersealing and jet grouting practice, the function of
the drainage culvert can be not influenced
during and after jet grouting.
3) The ground improvement project in urban area
is often carried out very close to the neighboringbuildings. Excess ground movement associatedwith jet grouting is a common phenomenon.

Figure 10. The photo of cut block within the improved area

2" drill hole
14
13

12

13

9

10 10 1111

11 10 10 12

8

7

7
8
6

6
5

2

2
4 3

3
1

5
3

4

1

6" drill hole(a) shield machines and operation platform set off(b) position drill holes, cut block and cut
section of acoustical wall

Figure 11. Shield machines taken apart and the cut section of acoustical wall8

6. ACKNOWLEDGMENT
The Authors are indebted to the following
organizations: Sanshin Corporation (Taipei Branch)for carrying out the field work of the V-JET
grouting; the Moh and Associate Inc. and the North
District Project office of Department of Rapid
Transit Systems, Taipei city government forproviding valuable construction records for thewriting of this paper.
7. REFERENCES
Georgios Anagnostou and Dimitrios Rizos (2009).
Geotechnical and contractual aspects of urban
tunneling with closed shields. ITA-AITES World
Tunnel Congress: Safe Tunelling for the City
and Environment, Budapest, Hungary.
Yong, D. M., Hayashi, K. and Chia, B. H. (1996).
Jet grouting for construction of a RC canal insoft marine clay. Grouting and deep mixing:
Procds., IS Tokyo 96, 2nd International
conferenceon
GroundImprovement
Geosystems Tokyo, Japan, pp 375-380.
Yoshida, H., Jimbo, S. and Uesawa, S. (1996).
Development and practical applications of large
diameter soil improvement. Grouting and deep
mixing: Procds., IS Tokyo 96, 2nd International
conferenceon
GroundImprovement
Geosystems Tokyo, Japan, pp721-726.
Takashi, M., Ikeda, A., Akira, Y., Yuukiti, T. andNakagawa, K. (2003). Evaluation method of soil
improvement effect of high-pressure injection
mixing method. Japan Society of Civil
Engineers, No. 735 (VI-59): 215-220.

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