TRENCHLESS TECHNOLOGY

Submitted By:

Abhimanyu saraswat

Civil 4th Year ‘A’

100107003

DATE OF SUBMISSION:- 29/11/2013

SUBMITTED TO:- PROF. SATYA PRAKASH HEAD OF DEPARTMENT CIVIL ENGINEERING

1)

TECHNICAL SEMINAR

REPORT

TITLE “Trenchless technology” is a type of subsurface construction

work that requires few trenches or no continuous trenches. It is

a rapidly growing sector of the construction and civil

engineering industry.

2)

ABSTRACT

The objective of this study is to understand about the new

advancement in civil engineering that is Trench less

technology. It include methods like installing, repairing and

renewing underground Pipes and cables using techniques

which minimize or eliminate the need for excavation. It can

reduce environmental damage, Social costs and produce an

alternative to open trench method of installation, renewal and

repair .It includes in, development of all kinds of underground

napping techniques, tunneling devices and specialist materials

and equipment. Trench less technology is basically making a

tunnel below the surface and staling service lines like water or

gas pipes, electric or telecommunication cables without any

disruption to the public. It also makes it possible to install the

utilities under rivers canals and other obstacles with no

disruption of flow and with minimum or no damage to the

environment.

The methods to be used in new

installation Micro tunneling, Horizontal directional drilling ,Short

drive system ,Guided drilling.

This detail study will show us why it is more advantages to use

trenchless technology compare to all others.

3)

KEYWORDS

o Pipe jacking,

o pipe ramming,

o horizontal boring,

o horizontal directional drilling

o trenchless construction

o guided boring

o Pipe eating

o Retaining the existing pipes

o Localized repair

o Pipe bursting

4)

OBJECTIVES

To find a substitute to conventional methods of digging

so that it is more easily, fast, reliable.

To improve the serviceability of pipes and decreases

the maintenance problems.

In brief, the objective of trenchless is to use it for Repair

& Retrofit of pipes, installation of new pipes, Reduction

of time, Structural safety & Reliability and Sustainability

& Environmental Protection.

Transmission is made easy and effective.

5)

STATE OF KNOWLEDGE

The current state of trenchless technology in india is the adoption of trenchless technology by Gas Authority of India Ltd has extensively used this system in laying the gas pipe lines from Gujarat gas fields to Northern India selectively for crossing roads and railway lines. In the past water supply and sewerage schemes were planned in Madras and Srinagar. But the projects did not start due to political and economic considerations. Currently, in Mumbai a sewerage project is under consideration using the micro-tunnelling method. It is hoped that the Mumbai Municipal Corporation will go ahead with the scheme soon. NBCC Ltd and its associate firms are trying to popularise trenchless technology by laying the MTNL fibre optic cables across roads and railway lines by using trenchless technology equipment. A technical committee under the aegis of NBCC Ltd will soon bring out a ‘National Guidelines for adopting trenchless technology in India’ similar to the ‘Yorkshire Code of Practice for Microtunnelling’ and the ‘Guidelines compiled by Louisiana Technical University, USA’.

6)

IMPORTANCE OF THE PROPOSED

SEMINAR

Traditional open cut trenches are in general use for laying the

underground services but have following inherent

disadvantages, which can be eliminated / minimised by

adopting the trenchless technology methods:

a) Traffic hindrance: Traffic obstruction, accidents, extra cost

in providing diversions and their maintenance etc.

b) Environment pollution: Dust and air pollution by vehicles

and machines, noise pollution to public, pollution of ground and

surface water etc.

c) Citizens and society: Increased cost in repair and

rehabilitating the roads, compensation for damages, advantage

of early availability of the utility and avoidance of public

hindrance etc.

Trenchless technology will prove competitive with its increased

use considering the social cost aspect in the project. For a

meaningful safe environment and public health in our cities the

application and adoption of this advance technology may soon

become imperative.

The seminar describes the few important methods for installing

utilities for infrastructural development under the ground.

7)

Methodology

Trenchless technology methods system have been categorized

in to two groups :

1) New installation

2) Rehabilitation and Renovation

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

MICRO TUNNELING:

Controlled excavation – steerable –Less than 1000mm

diameter –Medium length

Micro tunneling is a term which is used to describe remotely

controlled mechanical tunneling systems where the spoil is

removed from the cutting head with in the new pipe line which

is advanced by pipe jacking.

8)

Micro tunneling machines have now been developed to work

from drives hafts 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 for 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 tunneling is used extensively for 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 tunneling 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.

9)

HORIZONTAL DIRECTIONAL

DRILLING

Horizontal drilling systems are nowadays widely used for

installing pressure pipes under major obstacles such a motor

way intersections, large rivers and airports runways.

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 washover 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 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.

10)

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 pipe line. Auger boring is used in the

range of 100-1000mm diameter

11)

AUGUR 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.

ROD PUSHING:

It 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:

It is 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

12)

to 2000mm diameter can be laid using this technique

depending upon the equipment uses.

GUIDED DRILLING:

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 effects 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.

Guided Drilling

13)

REHABILITATION AND

RENOVATION

Methods including are:

1) Pipe bursting

2) Pipe eating

3) Retaining the existing pipes

4) Localized repair

Mini Burst

14)

PIPE BURSTING:

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.

PIPE EATING:

Pipe eating is an online micro tunneled 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.

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

15)

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.

LOCALISED REPAIR:

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 everyday from manhole

to manhole.

PIPE SLIP LINING:

It 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 in reduced diameter.

16)

MODIFIED SLIP LINING:

It 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.

17)

PRE-REQUISITES

Through surveys and site investigations are essential to the

success and efficiency of trench less installations and repair

techniques.

1) The survey results help top determine the most

appropriate systems.

2) The investigations methods include geophysical surveys,

boring and sampling, measurement of ground water table,

test pits and trenches, penetration tests, examinations and

investigations of existing structures using ground

penetration testing etc.

3) Closed circuit televisions, ground penetration radar, utility

detection equipments leak detection techniques are

available for below ground activities.

18)

The main trenchless techniques which are in use in India

(included in the above mentioned methods) are described

below.

DIRECTIONAL DRILLING:

Directional drilling involves steerable tunneling 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. The pilot hole is of

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 pushes 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

19)

positioned on rollers in line with the hole to minimize any axial

load on the line.

ADVANTAGES:

The major advantage is the speed of installation combined with

the minimum environmental and social impact.

1) 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.

2) Another advantage is that sufficient depth can be

accomplished to avoid other utilities.

3) Limitation of access and reception pits is another

advantage.

DISADVANTAGES:

1) Special equipment and very high degree of operation

skill is required.

20)

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.

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 spoil

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.

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.

ADVANTAGES:

The pipe ramming is an effective method for installing medium

size pipes. The method is economic since the equipment cost

21)

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.

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.

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 bullet or

shape. The method is restricted to relatively small diameter

lines in compressible soil conditions.

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

22)

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.

Moling Equipment

Pipe size is generally limited to 6 inches or less. However,

modern techniques in mole manufacturing have increased the

ability to make 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

23)

being optimum. Again span lengths have increased with

modern advances in mole design.

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

minimum.

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.

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.

24)

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.

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

25)

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.

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.

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.

26)

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 of this technology to be adopted in

mainly urban areas

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. Those are described below:

1) As the open trench is going to create obstruction roads,

busy areas, diversions have to be provided before start of

any digging word.

2) As the obstruction is created, the traffic has to be rerouted

causing traffic jams.

27)

Original users of the road have to undergo hardships in the

form of additional mileage as well as time.

Many a time, 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 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 through out and refilled

causing difficulties to the public; that is, cutting and refilling is

required at frequent times

28

ADVANTAGES OF NO-DIG

TECHNOLOGY

It reduces damages of valuable surface.

It reduces the danger of improperly compacted

excavations.

It saves resources.

It is accident free.

It avoids traffic jam.

It makes the use of the line(track) of the old pipe possible.

It saves underground space (pipe busting).

It reduces the impact on the environment.

It provides the hassle-free road surface.

It is possible to lay service lines across railway track,

narrow lanes etc. When open trenching is impossible.

Presence of a canal, pond, river etc. across the root poses

no problems to the trench less technology systems.

29)

UTILISATION OF RESEARCH

RESULTS

The use of Trenchless Technology for the installation of new, or the replacement or refurbishment of existing buried utilities have become well accepted over the past 25 years.

In this time many techniques have been developed including, soil displacement moles, pipe bursting, ramming, loose and tight fit insertion, directional drilling, pipeline relining and many more.

Today the techniques have become readily accepted and are often referred to as No-Dig or Limited Dig. They are now not only associated with reduced disturbance to the surrounding ground surface of a specific project, but are also seen as cost saving, and environmentally friendly with benefits including; reduced excavation size, lower infill and landfill requirements, increased safety, less noise and traffic disruption and much more.

30)

CONCLUSIONS

With all round developments in various fields like

petrochemicals where conveyance of gas, crude and refined

products over long distances is common, telecommunication

and power, water supply and sewerage etc. and mushrooming

growth of high- rise buildings in and in and around the cities is

becoming increasingly necessary that these lines are laid

underground leaving space above surface comparatively free.

i.e., Adoption of trench less technology is the only remedy.

Also if costs benefit analysis of the two systems (i.e. open

trenching methods and trenchelss technology methods) is

conducted, considering both direct and indirect costs, it will help

us make informed divisions on technology selection, under

different circumstances.

31)

REFERENCES

Jagadish Chandra, “Trenchless Technology in India: Need

of the New Millennium.” Civil Engineering and

Construction Review October 2009- page 48

Maninder Singh, “Techniques of Trenchless Technology

In Use In India.” Civil Engineering and Construction

Review October 2009- page 43

Dr.Neeraja Lugani Sethi, “Pre- Requisites for Trenchless

Technology.” Civil Engineering and Construction Review

October 2009- page 21

Sarkar A.K, “Trenchless Technology and INDSTT In

India.” Civil Engineering and Construction Review October

2009- page 13

The Construction Journal of India November 2009-

page21

32)