Trenchless Technology Technical Seminar Report

Trenchless Technology- A Review 2017-18
Dept. of Civil Engineering, BIT, Mangalore Page 1
Chapter 1
INTRODUCTION
1.1 GENERAL
Trenchless technology is the techniques for utility line installation, replacement,
rehabilitation, inspection, location and leak detection with minimum excavation from the
ground surface. It also makes it possible to install the utilities under rivers canals and other
obstacles with no disruption of flow and with minimum and no damage to the environment. It
can enhance forest roadway culvert applications by minimizing excavation and maybe less
costly than conventional open-cut excavation.
These techniques are currently used in urban areas in an age where environmental
degradation has become an ever-increasing concern. It involves creating new networks or
repairing existing ones by minimizing the impact on surface sites. This reduces the
inconvenience caused to the users by “open trench” work, which requires an excavation along
the full length of the area worked on.
It is necessary first it specify a definition which helps better determine the field of
application of this work. Of course, the “trenchless” is opposite of “open trench” work, but it
is also used for the installation of networks of small diameter, which are called
“inaccessible”, particularly where a worker cannot get into the networks in normal working
condition: it is generally accepted that the upper limit is approximately 1,200 mm in
diameter. We are interested in understand structures where the construction requires remote
controlled techniques because the site can neither be accessed from the surface (“trenchless”)
nor accessed from the inside (inaccessible).
1.2 OPEN TRENCH METHOD
It is a traditional method of trenching for laying the utility lines below the surface. In present
days, there are many disadvantages and difficulties in adopting this method, mainly in urban
areas.
These are described below:
 As the open trench is going to create obstruction roads, busy areas, diversions have to be
provided before the start of any digging word.

 As the obstruction is created, the traffic has to be rerouted causing traffic jams.
 The original users of the road have to undergo hardships in the form of additional mileage
as well as time.
 Many a times, while cutting deep trenches in congested areas appear in the adjacent
buildings.
 Another difficulty, which is encountered very often is the damage caused to other service
lines or cables present underground, providing temporary supports to these lines during
the construction is a cumbersome and costly affair.
 Trenches left open overnight should be fenced and barricaded. Hand of mechanical signs
should be used where necessary.
 While cutting open trenches, trees, shrubs, gardens etc. may have to be destroyed
damaging the environment.
 If any rehabilitation or renovation is required, the trenches once cut and refilled should
again be cut throughout and refilled causing difficulties to the public; that is, cutting and
refilling is required at frequent times
1.3 NEED FOR TRENCHLESS TECHNOLOGY
1. The disadvantages and difficulties encountered in conventional trenching methods have
resulted in thinking of the need for Trenchless Technology.
2. The advantages of the no-dig technology are also responsible for the need for this
technology to be adopted in mainly urban areas

Chapter 2
REVIEW OF LITERATURE
2.1 GENERAL
A critical literature review is presented which were contributed to the area of relevant topics
in relation to Trenchless technology. This review includes views, opinions, and suggestions
of scholars.
2.2 TRENCHLESS TECHNOLOGY
Mainak and Aarohi (2015) stated in their study that trenchless technology includes a wide
variety of methods, materials, and equipment capable of doing large scale works using
Tunnel Boring Machine or even small scale work like laying of pipes with or without the
entry of workers. This method is also very useful in seismic prone zone, places with hard
rock strata, high ground water level and can be helpful in reducing soil erosion in regions
with high rainfall. The method has also proven to be very useful for the army installations.
This method will prove to be very economic and time saving and will become a boon to a
third world and highly populated country like India.
Sai and Munasir, (2016) stated in their study that trenchless technology helps in installing,
repairing and replacing of water pipes, gas and petroleum pipes, and telecommunication
cables without disrupting the traffic, normal lifestyle and has minimal impact on economic
activity in congested areas and to the environment. This method is also very useful in seismic
prone zone, places with hard rock strata, high ground water level and can be helpful in
reducing soil erosion in regions with high rainfall. The method has also proven to be very
useful for the army installations. This method will prove to be very economic and time saving
and will become a boon to a third world and highly populated country like India.
Onkar and Kadam (2016) stated that Depending upon the specific situation trenchless
method can be cost-effective alternative to the more conventional open excavation. Fully
trenchless or partially trenchless technologies offer many benefits as a methodology for
rehabilitating or renewing pipelines. But in open cut excavation the social and environmental
impacts and the cost has considered. This study shortly discusses the comparisons of cost and

the factors that impact on a project and as per importance rating system developed between
open cut and trenchless techniques
2.3 SUMMARY
The above literature review not only helped in identification of the gap in the present body of
knowledge but has also enabled to establish relationship of the present study with what
already exist. Many studies and investigations were made by many scholars on Trenchless
Technology. This topic is selected on the basis of review of many research studies conducted
in abroad and in India. This literature review gives clear idea related to Trenchless
Technology. The main intention of the study is to investigate about the new trends in civil
engineering.

Chapter 3
CLASSIFICATION OF TRENCHLESS TECHNOLOGY
Trenchless technology methods systems have been categorized into two groups:
1. New installation
2. Rehabilitation and Renovation
3.1. NEW INSTALLATION
Methods for installation of a new pipeline or duct, including dealing with service connection
are:
1. Micro Tunneling
2. Horizontal Directional Drilling
3. Short Drive System
4. Guided Drilling
3.1.1 Micro Tunnelling
Controlled excavation – steerable –Less than 1000mm diameter –Medium length Micro
tunnelling is a term which is used to describe remotely controlled mechanical tunnelling
systems where the spoil is removed from the cutting head within the new pipeline which is
advanced by pipe jacking.
Figure 3.1: Micro Tunnelling
Micro tunnelling (Figure 3.1) machines have now been developed to work from drive shafts
in almost all types of ground conditions. The cutting head has to be carefully selected to deal
with the expected ground conditions, with the appropriate cutting tools and crushing devices
for the range of gravels, sands, slits, and clays.

The only excavating required from the service is to drive and receptions shafts. Spoil may be
removed from the face by an auger running through the newly installed pipeline to a skip in
the base of the drive shaft. Alternatively, water or bentonite may be used to convert the soil
into slurry at the cutting face. The slurry is less then pumped to the surface where the solids
are separated before disposal.
Micro tunnelling is used extensively in sewerage work where surface disruption has to be
minimized. Machines are now available to drive 100mm or more in soft ground for sizes
100mm diameter upwards. From drive shafts of less than 3mm diameter.
Micro tunnelling system has been developed in which temporary steel tubes are jacked in and
removed at the next manhole position, the new pipeline following in the established bore. In
micro tunnelling, the only indication on the surface is the presence of a control container with
A Hoist for Lowering Pipes into the Drive Shafts. Noise Levels And Traffic Disruption Are
minimized.
3.1.2 Horizontal Directional Drilling
Steerable heavy, powerful rig-Large size range –Long distances
Horizontal drilling systems (Figure 3.2) are nowadays widely used for installing pressure
pipes under Major obstacles such a motorway intersection, large rivers and airport runways.
Figure 3.2: Horizontal Directional Drilling
A small rotating and steerable drill bit is launched from the surface at an angle 10-15 and is
used to drill 90mm mud filled diameter hole. During the drilling operation a 125mm diameter
wash over pipe is drilled over the pilot string and following some 100mm behind the head.
Alternate drilling then continues on the pilot string is removed and the bore is enlarged by a
rotating barrel reamer attached to and pulled back by the wash over pipe, drilling mud being
used to llushed away the cuttings and to support the reamed hole. Subsequent caming

continues until the required diameter is achieved. The product pipe is less than attached to the
reaming head and pulled through the bore drives of more than 1.5km and of up to 1200mm
diameter have been carried out.
3.1.3 Short Drive Systems
 Auger Boring utilizes a rotating head to excavate the soil, which is transported by auger
flights operating in a casing to the drive pit. The head is recovered at an exit pit or in the
trench cut for the adjacent length of pipeline. Auger boring (Figure 3.3) is used in the
range of 100-1000mm diameter.
Figure 3.3: Auger boring
 Impact Moling in which a percussive mole is launched from a drive pit to displace the
soil and from a bore is widely used. The new conduct is normally drawn in behind the
mole. They are used to install services for all utilities.
Figure 3.4: Impact Moling
 Rod Pushing is a technique in which a bore of about 50mm diameter is formed by
displacement. A rod is advanced by a straight hydraulic push and the pilot hole may be
back reamed to the required size. The technique is used for the installation of pipes and
conduits up to 15mm diameter over lengths of 30-40mm.
 Pipe ramming and Thrust boring are similar processes where a casting, usually steel, is
driven through the ground from the drive pit to the exit pit. Accumulating spoil is

removed by compressed air and water after completing the bore. Pipe ramming is suitable for
most types of soil but not suitable where there are solid rock formations. It is said to be a cost
saving alternative to open trenching, angering or pipe jacking methods. Usually pipes up to
2000mm diameter can be laid using this technique depending upon the equipment uses.
3.1.4 Guided Drilling
Steerable small rig-Sallow drilling-Medium length.
Guide drilling employs an excavation or soil displacement with compact lightweight rig for rapid
mobilization. Small diameter jets mechanized cutting tools or displacement heads attached to a
flexible drill string are positioned to form a bore as the head is thrust forward. The drilling head is
launched from the surface at an inclined angle. Controlling the orientation of a slant face at the
head affects steering in both vertical and horizontal planes. Monitoring of the alignment takes
place using a transmitter in the head and a locating device at ground level. I having established
the pilot bore; back reaming equipment is drawn through the hole to enable it to accept the
product pipe, duct, or cable using an impact mole.
3.2 RENOVATION AND REHABILITATION
Methods including are:
a) Pipe bursting
b) Pipe eating
c) Retaining the existing pipe
d) Localized repair
3.2.1 Pipe Bursting
New for old without trenching – Size for size and upsize capability
In this method an existing pipeline can be replaced with a pipeline of the same or larger
dimension without opening up the ground. It is especially useful in areas where the load on
the system is more than the existing pipe can handle and replacement is required. The method
uses a mole as a bursting head that is drawn through the existing pipe crushing it as it moves
forward and replacing it with a new PE (polyethylene) pipe. The main advantage of this
system is that a small power source can be used to drive the mole with minimum time.

Upsizing from 100mm diameter to 225mm diameter is now well established, and pipes of up
to 600mm diameter have been replaced. Figure 3.5 shows pipe busting technique.
Figure 3.5: Pipe Bursting
3.2.2 Pipe Eating
New for old without trenching – Enlargement - Steerable
Pipe eating (Figure 3.6) is an online micro tunnelled replacement technique. The existing
defective pipeline is crushed and removed through the new pipeline. Lateral connections must be
disconnected in advance and may be replaced by rider sewers or reconnected by angled drilling.
Figure 3.6: Pipe Eating
3.2.3 Relining the Existing Pipes
This method requires access, usually by manholes, at both ends of pipe. A flexible liner is places
into the defective pipe and with the use of water under pressure finds its own way and can pass
bends of 90o
. In places where joints have moved or sections are missing, but the passage is
available, the liner creates a smooth transition. When the liner is in place, it is heat cured to create
a rigid, tough, and smooth inner surface.

3.2.4 Localised Repair
 Resin injection and chemical grouting at trouble spots
Local defects may be found in pipes due to cracking or joint failures. Systems are
available for resin injection to seal localized defects in the range 100mm-600mm
diameter. Chemical grouting with urethane and similar materials are used in sewer
rehabilitation. Remote and man entry grouting of defective joints and cracks may prevent
infiltration in pipelines.
This is an inexpensive method of rehabilitating existing systems up to several hundred
meters of length every day from manhole to manhole.
 Pipe Slip lining is another method used that involves inserting new smaller pipes in to
older, damaged sewers thereby replacing the old pipe. But the new pipe is reduced in
diameter.
 Modified slip lining often called close fit lining utilize the properties of PE or PVC to
allow temporary reduction in diameter or change in shape prior to insertion in the
defective pipe. The method includes Roll down, Swage lining and deformed lining. The
inserted pipe is subsequently expanded to form a tight fit against the wall of the original
pipe, thus avoiding the need for annular grouting as in conventional slip lining. For Roll
down and Swage lining, temporary reduction in diameter is achieved either by
mechanical rolling (Roll down) or drawing through a reduction die (Swage lining). For
Deformed linings, the pipe is deformed and folded immediately after extrusion and is
coiled on a drum. After insertion in the defective pipe, the lining is expanded using steam
and a re-rounding device to form a close fit. These systems are suitable where the
existing line is of good shape. As compared to conventional slip lining, in this method
there is little or no loss of hydraulic capacity.

Chapter 4
TECHNIQUES OF TRENCHLESS TECHNOLOGY IN
INDIA
The main Trenchless techniques which are in use in India are described below.
4.1 DIRECTIONAL DRILLING
Directional drilling involves steerable tunnelling systems for both small and diameter lines.
In most cases, it is a two-stage process. The first stage consists of drilling a small diameter
pilot hole along the desired centre line of a proposed line and in the second stage, the pilot
hole is enlarged to the desired diameter to accommodate the utility line and to pull the utility
line through the enlarged hole. Figure 4.1 shows Directional drilling method.
Figure 4.1: Directional Drilling
The pilot hole is approximately 3 inches in diameter and is drilled with a specially built rig up
with an inclined carriage typically adjusted to between 5 and 30 degrees, which push the drill
rods into the ground. However the optimum angle is 12 degrees. As the pilot hole is being
drilled, bentonite-drilling mud is pumped down the center of the drill rods. The drill head
consists of either a jetting head or drill bit. In the case of a jetting head, small diameter high-
pressure jets of bentonite actually cut the soil and facilitate spoil removal by washing the
cuttings to the surface where they settle out in a reception pit. In case of drill bit, the bit is
driven by a down hole mud motor located just behind the drill bit from energy derived from
the pumped drilling fluid. Before the start of back reaming the pipeline has to be positioned
on rollers in line with the hole to minimize any axial load on the line.
4.1.1 Advantages
1. The major advantage is the speed of installation combined with the minimum
environmental and social impact.

2. Long and complicated crossings can be accomplished with a great degree of accuracy
since it is possible to monitor and control the drilling operation so that utilities can be fit
into small corridors where little place is available between existing utilities.
3. Another advantage is that sufficient depth can be accomplished to avoid other utilities.
4. Limitation of access and reception pits is another advantage.
4.1.2 Disadvantage
1. Special equipment and very high degrees of operation skill is required.
2. As the cost of the equipment and the operation are high, bore length should be sufficient
in order for it to be economical.
3. Mainly steel pipe is being installed by the method.
4.2 RAMMING
In this method, the pipe is rammed through the soil by using a device attached to the end of
the pipe to drive the pipe through the soil. In this method, the tool does not create a borehole.
It acts as a hammer to drive the pipe through the soil. Compressed air supplied from an air
compressor is generally used as a power source. When ramming pipe, the leading edge cuts a
borehole, the spoils enters the pipe and is compacted as it is being forced to the rear of the
pipe. After the whole length of the pipe is rammed in place, the tool is removed and the pipe
is cleaned out. Figure 4.2 shows Ramming Technique.
Figure 4.2: Ramming
The type of pipe installed by the pipe ramming method is limited to steel due to the
application of cyclic impact loads on the pipe. The size of the pipe ranges from 2 inches to 55
inches. This method is capable of installing pipes to over 200 feet (60 meters) in length.

4.2.1 Advantages
The pipe ramming is an effective method for installing medium size pipes. The method is
economic since the equipment cost is not very high and the operation is simple. The pipe can
be installed in one piece or segments. This can be used in almost all types of soils. The
method does not require any thrust reaction structure.
4.2.2 Disadvantages
The major disadvantage is that there is no control over the line and grade and in case of
obstructions like boulders, the pipe may be deflected. Then work should be stopped
immediately. For small diameter pipelines, the method is economical, but for large diameter
pipes, the equipment cost is high.
4.3 MOLING
Moling is a method, which forms the borehole by compressing the earth that immediately
surrounds the compacting device which is an underground piercing (mole) is propelled by a
power source. The tool is streamlined into a bullet or shape. The method is restricted to
relatively small diameter lines in compressible soil conditions. Figure 4.3 shows Moling
Technique.
Figure 4.3: Moling
Compressed air or hydraulic fluid, transmitted to the toot through the flexible hoses, imparts
energy at a blow frequency of 100 to 600 strokes per minute to a reciprocating piston located
inside the nose of the tool. This action results in the tool propelling itself through the ground.
It is applicable in most ground conditions from loose sand to firm clay. The method required
the use of boring and receiving pit. After the operation the unit can be backed out of the
borehole. The tool is removed and the cable is attached to the air hose and pulled back

through the borehole. In the case of rigid pipe, it can simply be pushed through the open
borehole. Any type of pipe or cable can be installed by the method.
Pipe size is generally limited to 6 inches or less. However, modern techniques in mole
manufacturing have increased the ability to make the bores of large sizes. Even though 200
feet (60 meter) bores have been successfully made by this method, the span lengths were
limited to 60 feet (18 meter) with 40 feet being optimum. Again span lengths have increased
with modern advances in mole design.
4.3.1 Advantages
It is a rapid, economic, and effective method of installing small diameter lines. Any type of
utility line can be installed using the method. The stability of the soil around the borehole is
increased due to compaction. The investment in equipment is minimized.
4.3.2 Disadvantages
Compaction methods are limited in their length by reliability because basic systems are
unintelligent, unguided tools that tend to bury themselves, surface in the middle road or
damage existing utility lines.
4.4 AUGER BORING
The auger horizontal earth boring is a process of simultaneously jacking casing through the
earth while removing the spoil inside the casing by means of a rotating flight auger. The
auger is a flighted tube having dual functions, firstly it has couplings at each end that transmit
torque to the cutting head from the power source located in the bore pit and secondly, it
serves to transfer spoil back to the machine. Figure 4.4 Shows Auger Boring.
Figure 4.4: Auger Boring

4.4.1 Augur Blades
This method requires bore pit both at the entry and exit points of the bore. The auger-boring
machine consists of the boring machine, casing pipe, cutting head and augers as the major
components. The power source creates the torque, which rotates the auger, which in turn
rotates the cutting head. The cutting head cuts the soil and the soil is transported to the
machine through the casing by means of the auger, which acts as a screw conveyor. Figure
4.5 shows Auger Blades.
Figure 4.5: Auger Blades
The pipe size that can be installed by this method ranges from 4 inches (100mm) to over 60
inches (1500 mm). However, the most common size range is 8 inches(200 mm) to 36
inches(900 mm) and the average bore length ranges between 53 meter and 68 meter, though
with experience and the use of latest techniques up to 180 meter of boring is possible using
auger boring.
4.4.2 Advantages
The major advantage is that the casing is installed at the same time as the borehole excavation
takes place. This method can be used in a wide variety of soil types.
4.4.3 Disadvantages
This method requires different sized cutting heads and auger sizes or each casing diameter,
which increases the investment in equipment. The investment in bore, pit construction, and
the initial setup is also required. In case of soils containing large boulders, this method cannot
be used advantageously.

4.5 ADVANTAGES OF TRENCHLESS TECHNOLOGY
1. Less disturbing – By open cut method disturb local properties over agricultural land or
disturbing local highways. But by use of Trenchless technology come out from these
problems like landscape damage.
2. Less time – open cut method is time consuming method. In this method time is required
for the excavation and refilling of trenches. This process also means time is taken in site
restoration, spoils storage and traffic control.
3. Enhanced safety compared to steep excavations – by steep excavation Landslides can
be occurs. Where the mud is likely to subside due to steep walls or water aggravation,
protection needs to be taken with specialist equipment. By trenchless technology
provided safety to the workers as there are no steep trenches involved in this work.
4. Save time and cost related to survey and design – open cut method consist of
preliminary survey, detailed survey etc. In detailed survey consist of the depth of the
cut, the ground conditions where the trenches will run and also how much dewatering
will need to take place, ensuring that conditions are safe to work. But in trenchless
technique saved time and cost related to survey.
5. Encountering fewer unknowns in the ground – in open cut method, approximately
70% of the cost required for excavating and replacing the ground during the process. As
per unknowns come in the excavation or digging cost of excavation increases. By use of
Trenchless technology reduced this problem.
6. Minimize chance of disturbing existing utilities – at the time of open cut most
important problem come in front of is disruption to above surface activities. As well as
at the time of digging has to avoid existing utilities. Trenchless technology comes with
the ability to install new pipelines and rehabilitate existing pipelines with limited
disturbance to traffic and business activities, reduce damage to existing paved surfaces.
7. Problem to the public such as noise and air pollution – The indirect social costs of
open cut projects consist of unhealthy, inconvenience to traffic, and noise pollution. But
these problems can play a big part of local communities. These problems can be
overcome with trenchless technology without the need for road closures, noise
pollution.

Chapter 5
CASE STUDY
Case Study: Khan Market, New Delhi, OFC (Optical Fiber Cable)
Project Name: Horizontal Directional Drilling.
Client: Mahanagar Telephone Nigam Limited (MTNL)
Requirements: Installation of 20cm diameter optical fiber cable to supply 4G line.
Distance: 100m
Crossing: Underneath the road and old Museum.
Pit Size: Launch pit 4.5m x 1.5m
Constraints: Fully enclosed Garden at the centre of the museum with all plant and equipment having
to be transported through the public galleries to the job site. Cable to be installed to connect the
enclosed garden to a service area in a basement 12m away. The cable route would be beneath the
public gallery with installation being completed during the museum‟s opening hours. Space in the
basement was extremely limited making any method requiring access to both ends of the bore
impossible. The cable needed to be installed just 200mm below the buildings foundations. Figure
5.1 shows Pipe Ramming in underneath the road and old Museum in Khan Market, New
Delhi, and OFC
Ground Conditions: Hard packed soil and gravel.
Installation Time: 2 Days
Figure 5.1: Pipe ramming in underneath the road and old Museum in Khan Market,
New Delhi, and OFC

SUMMARY
1. The open cut trenching methods create road closures, traffic delays, noises and
general disruption.
2. This makes repair and rehabilitation of subsurface utilities difficult, particularly in
areas congested with traffic and buildings.
3. Lack of repair and rehabilitation of the pipeline for the water disruption and sewage
systems lead to leakages and waste water seepages, resulting in the contamination of
water distribution system and groundwater.
4. These problems often give rise to related health and environmental impacts.

REFERENCE
1. Hemishkumar, P., Jayeshkumar, P., Bhavsar, J. J., (2014), “, pp. 1-13. A Study On
Trenchless Technology: Eliminate The Need For Excavation”, National Conference
On-trends And Challenges Of Civil Engineering In Today's Transforming World
2. Onkar, K. C and Kadam, V. S., (2016), “Comparative Study Of Traditional Method
And Innovative Method For Trenchless Technology: A Review”, Internationa
Research Journal Of Engineering And Technology,Volume. 03, Issue. 05, pp. 1104-
1107.
3. Umesh, D and Norman, J., (2011), “Trenchless technology – An Overview”,
International Conference on Underground Space Technology, Bangalore, pp. 1-10.
4. Mainak, M P and Arohi, K M., (2015), “Trenchless Technology”, Civil Engineering
Systems and Sustainable Innovations, pp. 156-163.
5. Sai, K. D and Munasir, M., (2016), “Study of Trenchless Technology”, International
Journal of Scientific Research in Science Engineering and Technology, Volume. 02,
Issue. 06, pp. 43-48.

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