Micro-Tunnelling: Productivity improvement for Asset and Apparatus Owners.

Micro-Tunnelling
Trenchless and no-dig technology substitute talk with insight for
productivity improvement.

Table of Contents
01: Introduction
02: Principles
03: Procedure
04: Utilites And Applications
05: Productivity of Process
06: Benefits As Compared To Open Cut Construction
06.1: Site Rehabilitation
06.2: Construction Costs
06.3: Social Costs
06.4: Ground Conditions
06.5: Deep Excavation
06.6: Barriers:(Surface or Subsurface)
07: Environmental impact: health and safety
07.1: A Cleaner Process
07.2: A Safe Working Environment
07.3: Vacuum Extraction System
08: Programme Management
09: Conclusion
10: References
11: Author

Introduction
Micro-tunnelling started initially in Japan and Europe and came to the U.S in 1984. By
U.S. standards it is defined as a remotely controlled, laser-guided pipe jacking method
without any manpower for the excavation entry process. Pipes of various sizes can be
installed by this method. The tunnels are usually of very small diameters (from 368mm
up to 865mm), and that’s why this method is termed micro-tunnelling. [1] Micro-
tunnelling is a trenchless technology method used for installing new pipelines.
Theinherentadvantagesofthismethodoveropen-cuttrenchinghaveledtoitsincreasing
usesinceitsfirstintroductionintheearly1980s.Withthistechnology,surfacedisruption
can be minimized, especially in urban areas, and high accuracy of installation (usually
less than 2cm over 100m) can be achieved in both line and grade.
But micro-tunnelling machines are very expensive, and few contractors have extensive
experience with this technology.Micro-tunnelling can also be risky when unexpected
obstacles or soil changes occur. Careful constructability analysis is needed, and an
appropriate micro-tunnelling method should be selected to achieve the successful
completion of micro-tunnelling projects.
A series of tables for micro-tunnelling are included to support decision-making for
contractors who want to bid on micro-tunnelling projects. When the user checks
basic information about the potential project such as drive length, installation depth,
pipe diameter, and soil condition, the tables will give you adequate information to be
able to evaluate whether micro-tunnelling will be economically feasible and suggests
appropriate types of micro-tunnelling equipment.The user can then select micro-
tunnelling machines, types of pipes, and types of shaft construction methods. This
paper will be most beneficial when used at the preplanning stage by utility contractors.
Figure 1: Micro-tunneling site
1.5 million
kilometres
£1.2 bn
Of accidental strikes
on underground
pipes and cables
per year.
Of underground
services in the UK.

Figure 2:Project site for Micro tunneling
The whole process is operated from a control
cabin by one man only. The jacking pipe is
pushed behind a thrust boring machine from
a launch shaft by the main jacking station
located in the drive shaft up to the reception
shaft. At the same time an unmanned,
remote-controlled micro-tunnelling machine
excavates the tunnel face, the excavated
material to be transferred by the hydraulic
conveying system (slurry system) outside
the tunnel and to the separation system at
ground level. All these activities can be done
while the operator is inside the control cabin
monitoring and controlling the parameters.
Principles:
Procedure:
• The main jack pushes the MTBM through
the launching eye.
• After the MTBM is pushed into the
ground, disconnect the slurry lines and
hydraulic hoses from the MTBM. Retract
the hydraulic jacks.
• Lower a new pipe segment to the driving
shaft. Connect the slurry lines and
hydraulic hoses in the new pipe segment to
the ones in the previously jacked segment
(or MTBM).
• Jack the new pipe segment and excavate,
while removing the spoil. Excavate and
prepare the receiving shaft.
• Repeat steps 5 to 7 as required until the
pipeline is installed and MTBM reaches
the reception side.
• Remove the MTBM from the receiving
shaft. Remove the jacking frame and other
equipment from the driving shaft. Grout
the annular space between the exterior
pipe surface and the tunnel.
• In the case of sewer applications, install
manholes at the shaft locations. Remove
• Excavate and prepare the driving shaft.
• Set up the control container and any other
auxiliary equipment beside the jacking
shaft. Set up the jacking frame. Lower the
MTBM into the driving shaft and set it up.
• Set up a laser guidance system and the
MTBM in the driving shaft. Set up and
connect the slurry lines and hydraulic
hoses on the MTBM.
Figure 3: Site engineer working with the tunneling equipment
“The method of micro-tunnelling comes with many advantages
compared to other methods. In addition to the features such as faster
and more precise progress compared to the open-cut methods,
carbon emissions, noise, pollution, vibration, and environmental
nuisance are lesser disruptive.”

Utilities & Applications:
The major applications include:
• To construct water, gas, and oil pipelines.
• To install telecommunications and electricity cable lines.
• To construct culverts.
• To reduce the surface disturbance.
• To provide a persistent underground tunnel construction.
• To construct new or replace already existing sewerage
services.
• Totacklehurdleslikerailways,motorways,rivers,buildings,
canals, and airfields in the path of pipe laying projects. [2]
Productivity of process:
Micro-tunnelling is a complex operation that requires
the integration of several systems, a variety of supporting
equipment and personnel, and is heavily influenced by
subsurfacecondition.Theobjectiveofthisresearchistoanalyse
and evaluate the factors that affect the productivity in micro-
tunnelling operations. Computer simulation can be used to
study micro-tunnelling operations before they are actually
performed, thereby identifying operational inefficiency at
different stages of the project and finding soil impact on the
productivity.
The productivity of micro-tunnelling relates to many factors.
Soil situations, lubricate application, operator’s experience,
barriers, proper geotechnical analysis, and the capacity of
main jacks have the most impact on the productivity of
micro-tunnelling. These factors are critical for productivity
and are correlated. Therefore, the contractor must carefully
consider all of them in the bidding stage of the project. With
regards to soil type, sand is highly acceptable and gravels are
highly unacceptable. So, the contractor should analyze the
circumstancesandplanproperlytoachievehigherproductivity
rates. [6]
Figure 4: Microtunneling in construction site

Type of Soil Diameter
OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
m/shift m/day ETA drive length
(day)
Time for drive
(hours)
Organic alluvial clays and peats 368 80 45 61.70 148.08 0.54 12.97
Normally consolidated clays 368 80 45 54.92 131.80 0.61 14.57
Topsoil 368 80 45 51.30 123.12 0.65 15.59
Chalk 368 80 45 47.08 112.99 0.71 16.99
Very weak rock 368 80 45 47.08 112.99 0.71 16.99
Sandstone 368 80 45 41.91 100.58 0.80 19.09
Weak rock 368 80 45 40.37 96.88 0.83 19.82
Weathered overconsolidated clays 368 80 45 34.84 83.63 0.96 22.96
Concrete unreinforced up reinforced to 100kg/m3
368 80 45 33.20 79.68 1.00 24.10
Shale 368 80 45 31.98 76.74 1.04 25.02
Moderated weak rock 368 80 45 31.98 76.74 1.04 25.02
Boulder clay 368 80 45 28.46 68.31 1.17 28.11
Moderated strong rock 368 80 45 27.42 65.80 1.22 29.18
Concrete with reinforcement from 50kg/m3
to 75kg/m3
368 80 45 26.90 64.56 1.24 29.74
Unweathered overconsolidated clays (London Clay) 368 80 45 25.33 60.80 1.32 31.58
Sandstone 368 80 45 25.33 60.80 1.32 31.58
Keuper Marl (moderately weathered) 368 80 45 23.67 56.80 1.41 33.80
Reinforced Concrete average 100kg/m3
368 80 45 23.67 56.80 1.41 33.80
Limestone 368 80 45 23.67 56.80 1.41 33.80
Shallow Basalt 368 80 45 23.06 55.34 1.45 34.69
Marble 368 80 45 23.06 55.34 1.45 34.69
Shallow Granite 368 80 45 22.11 53.06 1.51 36.19
Strong rock 368 80 45 21.72 52.13 1.53 36.83
Concrete with reinforcement over 150kg/m3
368 80 45 20.53 49.26 1.62 38.97
Granite 368 80 45 19.33 46.40 1.72 41.38
Basalt 368 80 45 19.33 46.40 1.72 41.38
Slate 368 80 45 19.33 46.40 1.72 41.38
Hard rock 368 80 45 19.33 46.40 1.72 41.38
Quartzite 368 80 45 17.99 43.18 1.85 44.47
Steel 368 80 45 17.14 41.13 1.95 46.68
OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 368 80 45 40.37 96.88 0.83 19.82
Chalk 368 80 45 40.37 96.88 0.83 19.82
Very weak rock 368 80 45 33.20 79.68 1.00 24.10
Sandstone 368 80 45 31.98 76.74 1.04 25.02
Weak rock 368 80 45 28.46 68.31 1.17 28.11
368 80 45 27.42 65.80 1.22 29.18
Shale 368 80 45 25.33 60.80 1.32 31.58
Boulder clay 368 80 45 23.67 56.80 1.41 33.80
to 75kg/m3
368 80 45 22.36 53.67 1.49 35.77
Sandstone 368 80 45 21.72 52.13 1.53 36.83
368 80 45 21.06 50.55 1.58 37.98
Limestone 368 80 45 19.33 46.40 1.72 41.38
Shallow Basalt 368 80 45 19.33 46.40 1.72 41.38
Marble 368 80 45 19.33 46.40 1.72 41.38
Shallow Granite 368 80 45 19.33 46.40 1.72 41.38
Strong rock 368 80 45 17.99 43.18 1.85 44.47
368 80 45 17.68 42.44 1.88 45.24
Granite 368 80 45 17.21 41.29 1.94 46.49
Basalt 368 80 45 17.14 41.13 1.95 46.68
Slate 368 80 45 16.57 39.77 2.01 48.27
Hard rock 368 80 45 16.57 39.77 2.01 48.27
Quartzite 368 80 45 16.07 38.58 2.07 49.77
Steel 368 80 45 16.07 38.58 2.07 49.77
Minimum Stiffness MPa Maximum Stiffness MPa
3.17
meters per
hour
2.95
meters per
hour
3.99
meters per
hour
5.97
meters per
hour
Of average drive rate
in chalk
in London clay
in moderate weak
rock
in sandstone

OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 410 100 45 41.33 99.19 1.01 24.20
Chalk 410 100 45 37.93 91.03 1.10 26.36
Very weak rock 410 100 45 37.93 91.03 1.10 26.36
Sandstone 410 100 45 33.67 80.81 1.24 29.70
Weak rock 410 100 45 32.52 78.04 1.28 30.75
410 100 45 26.75 64.19 1.56 37.39
Shale 410 100 45 25.76 61.83 1.62 38.82
Boulder clay 410 100 45 22.93 55.04 1.82 43.61
to 75kg/m3
410 100 45 21.67 52.01 1.92 46.14
Sandstone 410 100 45 20.41 48.99 2.04 48.99
410 100 45 19.07 45.76 2.19 52.45
Limestone 410 100 45 19.07 45.76 2.19 52.45
Shallow Basalt 410 100 45 18.58 44.59 2.24 53.82
Marble 410 100 45 18.58 44.59 2.24 53.82
Shallow Granite 410 100 45 17.81 42.74 2.34 56.15
Strong rock 410 100 45 17.50 41.99 2.38 57.15
410 100 45 16.54 39.69 2.52 60.47
Granite 410 100 45 15.58 37.38 2.68 64.20
Basalt 410 100 45 15.58 37.38 2.68 64.20
Slate 410 100 45 15.58 37.38 2.68 64.20
Hard rock 410 100 45 15.58 37.38 2.68 64.20
Quartzite 410 100 45 14.55 34.92 2.86 68.73
Steel 410 100 45 13.80 33.13 3.02 72.44
OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 410 100 45 32.52 78.04 1.28 30.75
Chalk 410 100 45 32.52 78.04 1.28 30.75
Very weak rock 410 100 45 26.75 64.19 1.56 37.39
Sandstone 410 100 45 25.76 61.83 1.62 38.82
Weak rock 410 100 45 22.93 55.04 1.82 43.61
410 100 45 22.09 53.01 1.89 45.28
Shale 410 100 45 20.41 48.99 2.04 48.99
Boulder clay 410 100 45 19.07 45.76 2.19 52.45
to 75kg/m3
410 100 45 18.02 43.24 2.31 55.50
Sandstone 410 100 45 17.50 41.99 2.38 57.15
410 100 45 16.97 40.72 2.46 58.93
Limestone 410 100 45 15.58 37.38 2.68 64.20
Shallow Basalt 410 100 45 15.58 37.38 2.68 64.20
Marble 410 100 45 15.58 37.38 2.68 64.20
Shallow Granite 410 100 45 15.58 37.38 2.68 64.20
Strong rock 410 100 45 14.55 34.92 2.86 68.73
410 100 45 14.25 34.19 2.92 70.19
Granite 410 100 45 13.86 33.27 3.01 72.13
Basalt 410 100 45 13.80 33.13 3.02 72.44
Slate 410 100 45 13.35 32.04 3.12 74.90
Hard rock 410 100 45 13.35 32.04 3.12 74.90
Quartzite 410 100 45 12.95 31.08 3.22 77.22
Steel 410 100 45 12.95 31.08 3.22 77.22
2.55
meters per
hour
2.38
meters per
hour
3.22
meters per
hour
4.74
meters per
hour
in chalk
in London clay
in moderate weak
rock
in limestone

OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 565 100 45 21.76 52.23 1.91 45.95
Chalk 565 100 45 19.97 47.94 2.09 50.06
Very weak rock 565 100 45 19.97 47.94 2.09 50.06
Sandstone 565 100 45 17.78 42.67 2.34 56.25
Weak rock 565 100 45 17.12 41.10 2.43 58.40
565 100 45 14.08 33.80 2.96 71.00
Shale 565 100 45 13.57 32.56 3.07 73.71
Boulder clay 565 100 45 12.07 28.98 3.45 82.82
to 75kg/m3
565 100 45 11.41 27.39 3.65 87.63
Sandstone 565 100 45 10.75 25.80 3.88 93.04
565 100 45 10.04 24.09 4.15 99.62
Limestone 565 100 45 10.04 24.09 4.15 99.62
Shallow Basalt 565 100 45 9.78 23.48 4.26 102.20
Marble 565 100 45 9.78 23.48 4.26 102.20
Shallow Granite 565 100 45 9.38 22.51 4.44 106.63
Strong rock 565 100 45 9.21 22.11 4.52 108.54
565 100 45 8.71 20.90 4.78 114.83
Granite 565 100 45 8.20 19.68 5.08 121.94
Basalt 565 100 45 8.20 19.68 5.08 121.94
Slate 565 100 45 8.20 19.68 5.08 121.94
Hard rock 565 100 45 8.20 19.68 5.08 121.94
Quartzite 565 100 45 7.66 18.39 5.44 130.50
Steel 565 100 45 7.27 17.45 5.73 137.55
OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 565 100 45 17.12 41.10 2.43 58.40
Chalk 565 100 45 17.12 41.10 2.43 58.40
Very weak rock 565 100 45 14.08 33.80 2.96 71.00
Sandstone 565 100 45 13.57 32.56 3.07 73.71
Weak rock 565 100 45 12.07 28.98 3.45 82.82
565 100 45 11.63 27.91 3.58 85.99
Shale 565 100 45 10.75 25.80 3.88 93.04
Boulder clay 565 100 45 10.04 24.09 4.15 99.62
to 75kg/m3
565 100 45 9.49 22.77 4.39 105.40
Sandstone 565 100 45 9.21 22.11 4.52 108.54
565 100 45 8.94 21.45 4.66 111.90
Limestone 565 100 45 8.20 19.68 5.08 121.94
Shallow Basalt 565 100 45 8.20 19.68 5.08 121.94
Marble 565 100 45 8.20 19.68 5.08 121.94
Shallow Granite 565 100 45 8.20 19.68 5.08 121.94
Strong rock 565 100 45 7.66 18.39 5.44 130.50
565 100 45 7.50 18.00 5.55 133.32
Granite 565 100 45 7.30 17.52 5.71 136.99
Basalt 565 100 45 7.27 17.45 5.73 137.55
Slate 565 100 45 13.35 32.04 3.12 74.90
Hard rock 565 100 45 13.35 32.04 3.12 74.90
Quartzite 565 100 45 12.95 31.08 3.22 77.22
Steel 565 100 45 12.95 31.08 3.22 77.22
1.34
meters per
hour
1.25
meters per
hour
1.69
meters per
hour
2.49
meters per
hour
in chalk
in London clay
in moderate weak
rock
in limestone

OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 665 120 45 15.71 37.71 3.18 76.38
Chalk 665 120 45 14.42 34.60 3.47 83.23
Very weak rock 665 120 45 14.42 34.60 3.47 83.23
Sandstone 665 120 45 12.83 30.80 3.90 93.50
Weak rock 665 120 45 12.36 29.67 4.04 97.07
665 120 45 10.17 24.40 4.92 118.03
Shale 665 120 45 9.79 23.51 5.10 122.52
Boulder clay 665 120 45 8.72 20.92 5.74 137.69
to 75kg/m3
665 120 45 8.24 19.77 6.07 145.69
Sandstone 665 120 45 7.76 18.62 6.44 154.67
665 120 45 7.25 17.39 6.90 165.59
Limestone 665 120 45 7.25 17.39 6.90 165.59
Shallow Basalt 665 120 45 7.06 16.95 7.08 169.92
Marble 665 120 45 7.06 16.95 7.08 169.92
Shallow Granite 665 120 45 6.77 16.25 7.38 177.21
Strong rock 665 120 45 6.65 15.97 7.52 180.38
665 120 45 6.29 15.09 7.95 190.89
Granite 665 120 45 5.92 14.21 8.45 202.70
Basalt 665 120 45 5.92 14.21 8.45 202.70
Slate 665 120 45 5.92 14.21 8.45 202.70
Hard rock 665 120 45 5.92 14.21 8.45 202.70
Quartzite 665 120 45 5.53 13.27 9.04 216.97
Steel 665 120 45 5.25 12.59 9.53 228.70
OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 665 120 45 12.36 29.67 4.04 97.07
Chalk 665 120 45 12.36 29.67 4.04 97.07
Very weak rock 665 120 45 10.17 24.40 4.92 118.03
Sandstone 665 120 45 9.79 23.51 5.10 122.52
Weak rock 665 120 45 8.72 20.92 5.74 137.69
665 120 45 8.40 20.15 5.96 142.94
Shale 665 120 45 7.76 18.62 6.44 154.67
Boulder clay 665 120 45 7.25 17.39 6.90 165.59
to 75kg/m3
665 120 45 6.85 16.43 7.30 175.25
Sandstone 665 120 45 6.65 15.97 7.52 180.38
665 120 45 6.45 15.48 7.75 186.00
Limestone 665 120 45 5.92 14.21 8.45 202.70
Shallow Basalt 665 120 45 5.92 14.21 8.45 202.70
Marble 665 120 45 5.92 14.21 8.45 202.70
Shallow Granite 665 120 45 5.92 14.21 8.45 202.70
Strong rock 665 120 45 5.53 13.27 9.04 216.97
665 120 45 5.42 13.00 9.23 221.59
Granite 665 120 45 5.27 12.65 9.49 227.70
Basalt 665 120 45 5.25 12.59 9.53 228.70
Slate 665 120 45 5.08 12.18 9.85 236.43
Hard rock 665 120 45 5.08 12.18 9.85 236.43
Quartzite 665 120 45 4.92 11.82 10.16 243.72
Steel 665 120 45 4.92 11.82 10.16 243.72
0.97
meter per
hour
0.90
meter per
hour
1.22
meters per
hour
1.80
meters per
hour
in chalk
in London clay
in moderate weak
rock
in limestone

OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 780 140 45 11.42 27.40 5.11 122.61
Chalk 780 140 45 10.48 25.15 5.57 133.58
Very weak rock 780 140 45 10.48 25.15 5.57 133.58
Sandstone 780 140 45 9.33 22.39 6.25 150.07
Weak rock 780 140 45 8.99 21.57 6.49 155.80
780 140 45 7.39 17.73 7.89 189.48
Shale 780 140 45 7.12 17.08 8.20 196.68
Boulder clay 780 140 45 6.34 15.21 9.21 220.96
to 75kg/m3
780 140 45 5.99 14.37 9.74 233.87
Sandstone 780 140 45 5.64 13.54 10.34 248.24
780 140 45 5.27 12.64 11.08 265.82
Limestone 780 140 45 5.27 12.64 11.08 265.82
Shallow Basalt 780 140 45 5.13 12.32 11.36 272.65
Marble 780 140 45 5.13 12.32 11.36 272.65
Shallow Granite 780 140 45 13.83 33.19 4.22 101.23
Strong rock 780 140 45 4.83 11.60 12.07 289.59
780 140 45 4.57 10.97 12.76 306.31
Granite 780 140 45 4.30 10.33 13.56 325.34
Basalt 780 140 45 4.30 10.33 13.56 325.34
Slate 780 140 45 4.30 10.33 13.56 325.34
Hard rock 780 140 45 4.30 10.33 13.56 325.34
Quartzite 780 140 45 4.02 9.65 14.51 348.31
Steel 780 140 45 3.81 9.16 15.29 366.99
OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 780 140 45 8.99 21.57 6.49 155.80
Chalk 780 140 45 8.99 21.57 6.49 155.80
Very weak rock 780 140 45 7.39 17.73 7.89 189.48
Sandstone 780 140 45 7.12 17.08 8.20 196.68
Weak rock 780 140 45 6.34 15.21 9.21 220.96
780 140 45 6.10 14.64 9.56 229.44
Shale 780 140 45 5.64 13.54 10.34 248.24
Boulder clay 780 140 45 5.27 12.64 11.08 265.82
to 75kg/m3
780 140 45 4.98 11.95 11.71 281.14
Sandstone 780 140 45 4.83 11.60 12.07 289.59
780 140 45 4.69 11.25 12.44 298.55
Limestone 780 140 45 4.30 10.33 13.56 325.34
Shallow Basalt 780 140 45 4.30 10.33 13.56 325.34
Marble 780 140 45 4.30 10.33 13.56 325.34
Shallow Granite 780 140 45 4.30 10.33 13.56 325.34
Strong rock 780 140 45 3.99 9.57 14.63 351.19
780 140 45 3.94 9.45 14.82 355.61
Granite 780 140 45 3.83 9.20 15.23 365.41
Basalt 780 140 45 3.81 9.16 15.29 366.99
Slate 780 140 45 3.69 8.85 15.81 379.47
Hard rock 780 140 45 3.69 8.85 15.81 379.47
Quartzite 780 140 45 3.58 8.59 16.31 391.37
Steel 780 140 45 3.58 8.59 16.31 391.37
0.07
meter per
hour
0.65
meter per
hour
0.89
meter per
hour
1.31
meters per
hour
in chalk
in London clay
in moderate weak
rock
in limestone

OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 875 140 55 11.09 26.62 5.26 126.23
Chalk 875 140 55 10.18 24.43 5.73 137.56
Very weak rock 875 140 55 10.18 24.43 5.73 137.56
Sandstone 875 140 55 9.06 21.74 6.44 154.55
Weak rock 875 140 55 8.73 20.94 6.69 160.45
875 140 55 7.18 17.23 8.13 195.05
Shale 875 140 55 6.91 16.59 8.44 202.50
Boulder clay 875 140 55 6.15 14.77 9.48 227.48
to 75kg/m3
875 140 55 5.81 13.96 10.03 240.77
Sandstone 875 140 55 5.48 13.15 10.65 255.57
875 140 55 5.12 12.28 11.40 273.70
Limestone 875 140 55 5.12 12.28 11.40 273.70
Shallow Basalt 875 140 55 4.99 11.97 11.70 280.77
Marble 875 140 55 4.99 11.97 11.70 280.77
Shallow Granite 875 140 55 4.78 11.47 12.21 292.99
Strong rock 875 140 55 4.70 11.27 12.42 298.13
875 140 55 4.44 10.65 13.14 315.42
Granite 875 140 55 4.18 10.03 13.96 335.10
Basalt 875 140 55 4.18 10.03 13.96 335.10
Slate 875 140 55 4.18 10.03 13.96 335.10
Hard rock 875 140 55 4.18 10.03 13.96 335.10
Quartzite 875 140 55 3.90 9.37 14.94 358.62
Steel 875 140 55 3.71 8.89 15.74 377.78
OD (mm)
Recommended
Drive length (m)
MTBM's Power
(Hp/kV)
(day)
Time for drive
(hours)
Topsoil 875 140 55 8.73 20.94 6.69 160.45
Chalk 875 140 55 8.73 20.94 6.69 160.45
Very weak rock 875 140 55 7.18 17.23 8.13 195.05
Sandstone 875 140 55 6.91 16.59 8.44 202.50
Weak rock 875 140 55 6.15 14.77 9.48 227.48
875 140 55 5.93 14.22 9.84 236.22
Shale 875 140 55 5.48 13.15 10.65 255.57
Boulder clay 875 140 55 5.12 12.28 11.40 273.70
to 75kg/m3
875 140 55 4.83 11.60 12.07 289.59
Sandstone 875 140 55 4.70 11.27 12.42 298.13
875 140 55 4.55 10.93 12.81 307.42
Limestone 875 140 55 4.18 10.03 13.96 335.10
Shallow Basalt 875 140 55 4.18 10.03 13.96 335.10
Marble 875 140 55 4.18 10.03 13.96 335.10
Shallow Granite 875 140 55 4.18 10.03 13.96 335.10
Strong rock 875 140 55 3.90 9.37 14.94 358.62
875 140 55 3.82 9.17 15.26 366.36
Granite 875 140 55 3.72 8.93 15.68 376.44
Basalt 875 140 55 3.71 8.89 15.74 377.78
Slate 875 140 55 3.58 8.60 16.28 390.65
Hard rock 875 140 55 3.58 8.60 16.28 390.65
Quartzite 875 140 55 3.47 8.34 16.79 402.89
Steel 875 140 55 3.47 8.34 16.79 402.89
0.68
meter per
hour
0.64
meter per
hour
0.86
meter per
hour
1.25
meter per
hour
in chalk
in London clay
in moderate weak
rock
in limestone

Theopen-cutmethodsneedwholetrenchestobedugtocoverpipelength.But
in micro-tunnelling, only one entry and exit pits are needed hence a smaller
site footprint. With respect to cost, specifically for dense-populated areas,
the reinstatement of surfaces such as pavement, sidewalks, and landscaping
are expensive. In micro-tunnelling, the costs of site rehabilitation are very
much minimized because lesser surface disruption is caused.
Site rehabilitation:
Benefits as compared to Open cut
construction:
Construction costs:
The Open-cut process requires large-scale digging and backfilling and
this results in longer project durations. Micro-tunnelling minimizes
construction costs by reducing the time required for labor and equipment.
Social costs:
The open-cut method leads to greater social costs in dense and congested
sites because of significant disturbance to the general public and businesses.
These social costs may be due to disturbance to traffic and business
activities, bad environmental impacts, current paved surfaces destruction,
and disruption to normal life patterns of the people living, shopping, and
working around the construction site. In micro-tunnelling, lesser social
costs are caused because of lesser surface disturbance.
Ground conditions:
For the open-cut process, rock excavation cost is very high, plus noise and
vibrations also pose threat to the nearby environment. But in the case of
micro-tunnelling, only one core is required to be drilled through rocks.
Therefore, micro-tunnelling proves to be a very appropriate substitute in
terms of cost and overall productivity.
One major concern is the dewatering cost required in wet flowing soils
specifically in sites where sheet piling is needed. Micro-tunnelling proves
economical in this case as well as only launch and exit pits need to be
dewatered. Contaminated ground is another issue where micro-tunnelling
has prominent cost benefits. Since in micro-tunnelling the excavation
requirement is relatively less, so the treatment cost is also less.
Figure 1: Concrete microtunneling pipes in an excavation pit
368
millimeter
410
millimeter
outer diameter outer diameter
565
millimeter
665
millimeter
780
millimeter
875
millimeter

Deep excavation:
Micro-tunnelling gets more effective if deep excavations are to be done. Contrary to open-cut
constructions, only slight project cost variation occurs with respect to excavation depth in
micro-tunnelling. Consequently, at certain depth down the ground micro-tunnelling becomes
more economical. Various parameters like soil conditions, job location, and other obstructions
govern this depth range. For instance, in an urban road reserve area it maybe 2m deep, and in
a greenfield setting more than 5m deep.
This action can provide complete records of Material Chemistry Verification for your pipeline
construction quality program and help mitigate corporate risk. Material Verification allows
for Objective Quality Evidence to regulate that MTR chemistry is being verified and increases
pipeline safety by reducing the chance of an incorrect material entering the construction
process of the finished product.
Barriers (surface or subsurface):
Micro-tunnelling comes with capability to build keyhole pipeline for sites with surface barriers
like hills, power poles, lakes, trees, roads, waterways, and other structures, and subsurface
hurdles including other facilities, foundations, and pylons. The keyhole pipeline includes
excavating a small shaft in locations within reach where hurdles can be tackled. This enables
pipe installation around any congestion, as very less excavation is required. [4]
Environmental impact: health and safety:
A Cleaner Process:
In micro-tunnelling, there is a prominent reduction of both incoming as well as outgoing
materials. This particular characteristic of micro-tunnelling makes it safer for workers and
also for the environment. Stone and soil backfill discharge proportions are highly reduced. In
micro-tunnelling, no liquids appear on the surface while injecting bentonite at high pressures.
This feature is especially useful for horizontal directional drilling. Hence micro-tunnelling is
overall a very clean and effective process for tunneling.
A Safer Working Environment:
To construct utilities within busy areas, through natural barriers, and underneath waterways,
major environmental concerns are raised. Construction companies want to minimize the
disturbance to these environments as much as possible – whilst of course, still getting the
job done effectively. Micro-tunnelling processes have proven to be an advantageous and
practical method that not only reduces environmental risks, but project costs too. In trenchless
construction, almost all micro tunnels and pipe jacks are installed between a drive shaft and
reception shaft. In order to prevent environmental contamination and the ingress of water
into the pipeline, a reception arrangement has to be designed to ensure the exit points are out
of the ground or set underwater. Micro-tunnelling innovations are specifically designed to
use the right size drive shafts to promote a successful pipe installation at virtually any depth,
through any soil type with as little disruption to the surrounding environment. Other safety
precautions that should be taken are checking piping and piping component material chemistry
with a handheld x-ray fluorescence analyzer (XRF) and producing “Trust but Verify” piping
and piping component material test reports (MTR’s).
Vacuum Extraction System:
The micro-tunnelling method uses a vacuum extraction system promoting a relatively cleaner
environment. This also gives consistent ground assistance by utilizing a pipe jack technique.
The setup footprint to the worksite is greatly reduced. Such an extraction process also ensures
safer methods of open-cut construction, to both the workers and the environment around us.
[3]
Programme Management:
Micro-tunnelling is done in the following stages:
• Planning;
a) Studying previous construction projects;
b) Making a physical sightline between shaft positions;
c) Considering current facilities and hurdles coming in tunnel route;
• Data Collection;
• Laboratory Testing;
• Geotechnical Reports;
• Bidding Documents;
• Construction [5].
Conclusion:
The micro-tunnelling technique has proved advantageous in every possible sense. Contrary
to open-cut methods, micro-tunnelling has improved traffic control, requires lesser digging
around current facilities, lesser social cost, lesser environmental disruption, and higher worker
safety. Although there exists a comprehensive and detailed process for implementing micro-
tunnelling, if done right this method can save both time and money. Hence in today’s world,
micro-tunnelling is by far the best construction methodology for tunnel constructions.

References:
1. http://www.subterra.us/engineering/tunneling/micro-tunneling/#toggle-
id-4
2. https://www.slideshare.net/jamalabed58/microtunneling-
presentation-2014
3. https://www.thermofisher.com/blog/mining/four-environmental-benefits-
of-microtunneling/
4. https://utilitymagazine.com.au/what-factors-make-microtunnelling-more-
cost-effective-than-traditional-open-cut-methods/
5. https://trenchlesstechnology.com/planning-construction-microtunneling-
projects/
6. Mohamed Y. Hegab & Ossama M. Salem (2010). Ranking of the
Factors Affecting Productivity of Micro-tunnelling Projects. Journal of
Pipeline Systems Engineering and Practice, 1(1)https://ascelibrary.org/
doi/10.1061/%28ASCE%29PS.1949-1204.0000038#
Author:
Carlo Gabriele Borri is a construction manager, project manager and senior
estimator/surveyorwithovertwentyyearsofInfrastructure,Transport,Utilities,
Civil Engineering, Tunnelling and Commercial. Throughout his career, he
has focused on building quality relationships with both his inhouse team and
business clients. Valuing a strong partnership in all aspects of business, Carlo
strives toward constant communication with members of his projects. As such,
his fluency in Italian, English, and German has earned him new collaborations
in new places.
As a member of several Professional’s Bodies, such as RIBA, CIArb, CIOB and
ICE, Carlo’s goal has been to maintain professionalism while furthering his
career. Starting out as a construction manager, his beginnings as a supervisor
were humble. He learned to oversee everything from purchasing to design. His
strengths in cost estimation and cost management have become his primary
role in recent years. Working with both premier construction and consultancy
firms in London, he has planned the development of numerous infrastructure
and commercial structures such as the HS2 Phase 1 for both Main Work Civils
Contract (MWCC) and Enabling Work Contract (EWC), Highways England
(HE) for A229/M2, Transport for London (TfL) Overground Surrey Quays
and DLR Beckton Park station upgrades, Network Rail (NR) Chiltern lane new
interchange station to Old Oak Common, Hogan Lovells fit-out, Deloitte fit-
out and the new Tesco Headquarter Heart Pavilion.

www.99underground.com
“Infrastructure: paving the way forward.”

Micro-Tunnelling: Productivity improvement for Asset and Apparatus Owners.

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