Construction Management,Tunneling in hard rock, Tunnel Boring machine, Drilling and Blasting, Shapes of the tunnel, Types of tunnels.

1. Project Report on
CASE STUDY ON TUNNELING IN HARD ROCKS
By
Ma.Mayur .U. Rahangdale
(202030018)
M. Tech (Construction Management)
2020 - 2021
Guided by
Prof. (Dr.) S.Y. Mhaske
Department of Civil and Environmental Engineering
Veermata Jijabai Technological Institute
(Autonomous Institute Affiliated to University of Mumbai)
Mumbai 400 019
2020 – 2021

2. 2
STATEMENT BY THE CANDIDATE
We wish to state that the work embodied in this report titled “CASE STUDY ON
TUNNELING IN HARD ROCKS” forms my contribution to the work carried out under the
guidance of Prof. (DR.) S.Y. Mhaske at the Veermata Jijabai Technological Institute.
This work has not submitted for any other degree or diploma of any university/ institute.
Wherever references have been made to previous works of others, it has been clearly
indicated.
Signature of the Candidate
MA.MAYUR .U. RAHANGDALE
(202030018)

3. 3
CERTIFICATE
This is to certify that MA.MAYUR .U. RAHANGDALE (202030018) the studentof
M-Tech.(Construction Management) Veermata Jijabai Technological Institute, Mumbai have
Successfully completed the project entitled “CASE STUDY ON TUNNELING IN HARD
ROCKS” During the academic year 2020-2021, Under the guidance of Prof.(Dr.) S.Y.
Mhaske.
Prof. (Dr.) S.Y. Mhaske DR. S.Y. MHASKE
(PROJECT GUIDE) PROF & HEAD
CIVIL & ENVIRONMENTAL
ENGG. DEPT

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ACKNOWLEDGEMENT
It is obvious that the development of project needs the support of many
people. Getting idea of analyzing a project, finalizing it as best one for me and above all
developing it successfully always is a job more than dozen of people. It is great pleasure for
me to acknowledge the assistance and contribution of my own effort. I had always been
grateful for the support that I got from all my surroundings with respect knowledge and
support.
I am very grateful to my Parents who have always being supportive of the
strange new twist and turns our life has taken. They are the one who have been the pioneer of
success and achievement in life and of course they have supported us rather directly or
indirectly in developing our project.
I sincerely acknowledge to my project guide Prof. (Dr.) S.Y. Mhaske whose
continuous encouragement and support enabled the project to materialized and contributed to
its success.
Finally, I thankful to all my Friends for their constant inspiration, support and
encouragement.
MA.MAYUR .U. RAHANGDALE
(202030018)

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ABSTRACT
Tunnels are very important structures which are being used in various constructions; like in
road, railway for defense purpose and laying of pipelines etc. Tunnels have different shapes
on the basis of their uses and the ground conditions and the availability of materials. All
tunnels have various degrees of complexity depending on function and safety needs or the
code requirements at the time of construction, but most tunnels employ one or many
functional systems, such as lighting, ventilation, drainage, fire detectors and alarms, fire
suppression, communications and traffic control. With the limited access and confined
conditions within a tunnel; the operation, maintenance and inspection of a tunnel must be
thoroughly regimented to provide an adequate level of safety for the traveling public.
Construction of different types of tunnels includes some very basic operations or steps which
are to be followed in sequence in order to build or to construct a tunnel. This are called basic
tunneling operations. These tunneling operations may differ in comparison to older times and
this modern time. This report provides information on tunnels and various tunneling
operations involved in hard rock and also provide information related to various shapes of
tunnels, their types, tunnel boring machine etc. case study is also there related to tunneling in
hard rock.

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TABLE OF CONTENTS
Chapter 1
Introduction
1.1 General…...........................................................................................................9
1.2 Objective of study…..........................................................................................9
Chapter 2
Literature review
2.1 Why Necessity of tunnel arises?…................................................................. 10
2.2 Factors to be considered in tunneling: ............................................................11
2.3 Tunnel Alignment...........................................................................................11
2.4 Selection of Tunnel alignment depends on.………,…...................................11
Chapter 3
Advantages and disadvantages of tunnels
3.1 Advantages of Tunnel.................................................................................... 12
3.2 Disadvantages ................................................................................................12
Chapter 4
Classification of Tunnels
4.1 On Purpose…................................................................................................13
4.2 On types of Ground …...................................................................................13
4.3 On the position and alignment...................................................................... 13

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Chapter 5
Shapes of Tunnels
5.1 Circular Shape Tunnel… .......................................................................... 15
5.2 D Shape Tunnel….....................................................................................15
5.3 Rectangular Shape Tunnel…..................................................................... 15
5.4 Egg- Shape Tunnel….................................................................................15
5.4 Elliptical Shape Tunnel…..........................................................................16
5.5 Horse shoe Tunnel… .................................................................................16
5.6 Pilot Tunnel…............................................................................................16
Chapter 6
Tunneling in Hard Rock
6.1 Methods…..................................................................................................17
6.2 Tunnel Boring Machine………………………………………………….19
6.3 Hard Rock TBMs…………………………………………………….......19
6.4 Drilling Blasting and Hauling of Muck…………………………………..20
6.5 Theory of drilling and Blasting…………………………………………..20
6.6 Drilling Equipment’s……………………………………………………..21
6.7 Blasting………………………………………………………………….. 25
6.8 Types of Explosive……………………………………………………….25
Chapter 7
Case Study on Maroshi –Ruperal water tunnel Mumbai
7.1 Introduction……………………………………………………………...29
7.2 Construction Process…………………………………………………….31
7.3 Conclusion………………………………………………………………32
References

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List of Figures
Figure
No
Description Page
4.1.1 Saddle or base Tunnel 13
4.1.2 Spiral Tunnel 14
5.1.1 Shapes of Tunnel 16
6.1.1 Heading and Benching Method 17
6.1.2 Drift Method 18
6.3.1 Hard rock tbms 19
6.4.1 Detonator 20
6.5.1 Placement of Explosive 21
6.8.1 Explosive 26
7.1.1 Longitudinal section and plan of tunnel from Maroshi to
Ruperal College.
30
7.2.1 Cutters position on cutter head of 3.6 m diameter 31
7.2.2 View of excavated tunnel face using TBM 31

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Chapter 1
Introduction
1.1 General
Tunnel is an artificial underground passage, especially one built through a hill or under a
building, road, or river. Tunnels are not only structures constructed of concrete, steel,
masonry, and timber (to a very limited degree) or bored in rock, but also use numerous
functional systems to perform roles for the tunnels to function properly.
To construct any tunnel through river or through a hill, or an underground tunnel, there is
certain operation or steps which are to be followed or to be performed, which are called
various tunneling operations.
A Tunnel is a underground passageway completely enclosed except for openings for exit
commonly at each end.
Tunnel construction for transport routes is becoming increasingly important worldwide.
Transport is accelerated and optimum protection is provided for the environment and the
landscape. Many tunnels are considered technological masterpiece and governments have
honored tunnel engineers as heroes. Constructing a tunnel, however, is one of the most
complex challenges in the field of civil engineering.
1.2 Objective of study
Tunnels are underground passages used for transportation. They could be used for
carrying freights and passengers, water, sewage; etc. Tunnels are more economical than
open cuts beyond certain depths. Tunnels avoid disturbing or interfering with surface life
and traffic during construction. Tunnels prove to be cheaper than bridges or open cuts to
carry public utility services like water, sewer and gas. Feasibility of these constructions in
natural materials, such as rock and soil, causes the geological conditions to play a major
role in their stability. Aspects of major importance and that are decisive for the feasibility
of a tunnel project is geological conditions, construction time and costs. The objective of
this lesson is to provide the general aspects of importance in tunnels, their types and
methods of tunneling.

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Chapter 2
Literature review
2.1 Why Necessity of tunnel arises?
Maintenance cost of tunnel is much less than that of bridge or a heavy cut.
The main reason behind provision of a tunnel is to eliminate a circuitous route for
reaching the other side of hill (the length of the railway line will be considerably
reduced).
In large cities, tunneling would provide the most rapid and unobstructed transportation
(leading to reduction in traffic congestion)
Tunnels provide flat gradients in hilly areas.
Economics of tunneling is a broad question and in general depends the relative cost of
open cut vs. tunneling. Generally when depth of cut is over 18 m, tunneling is advisable.
From view point of economy and traffic safety, the tunneling operation is desirable under
the following conditions…
a. To allow rapid and unobstructed transport facilities in big the congested cities.
b. To avoid acquisition of valuable land.
c. To avoid long circuitous routes around a mountain or spur.
d. To avoid sliding of open cut sides in softer soils.
e. To connect two terminal stations separated by mountain.
f. To divert water for generation of power.
g. To carry public utility services like oil, gas, water etc. across the stream or a
mountain.
h. To avoid the steep gradients in mountains and thereby maintain a high speed.
i. When the provision of the bridge over the river is costlier and in convenient.
j. It is preferred on routes of strategic importance because a tunnel is hidden in
ground.
k. To save the maintenance cost which is generally lesser for tunnel compared to a
bridge and an open cut.

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2.2 Factors to be considered in tunneling:
The following factors should be taken into consideration when selecting the method:
- Tunnel dimensions,
- Tunnel geometry
- Length of tunnel,
- Total volume to be excavated
- Geological and rock mechanical conditions
- Ground water level and expected water inflow
- Vibration restrictions &
- Allowed ground settlements.
2.3 Tunnel Alignment
Tunnel alignment is an important aspect in engineering constructions.
The primary objectives of the tunnel alignments are to:
• Reduce transit trip times;
• Increase quality and reliability of service; and
• Minimize impacts of surface transit operations in sensitive locations.
2.4 Selection of Tunnel alignment depends on
• Topography of area & points of entrance and exit,
• Selection of site of tunnel to be made considering two points.
• Alignment Restraints
• Environmental Considerations.

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Chapter 3
Advantages and disadvantages of tunnels
3.1 Advantages of Tunnel
• For carrying public utilities like water or gas, railway lines or roads across a stream or
mountain, tunnels may be cheaper than bridge or open cut.
• It is more efficient than bridges (as during wars it is much difficult to destroy a tunnel
compared to bridge).
• It is generally assumed that when the cut required will have a vertical depth exceeding 20
m; it is less expensive to build a tunnel.
• Tunnels avoid disturbing or interfering with surface life and traffic during construction
• Tunnels avoid traffic conjunction and provide rapid transportation in crowed cities.
• Tunnels connect two terminals stations by shortest route.
• Tunnels carry water to generate power.
• If tunnels are provided with easy gradients, the cost of hauling is decreased.
• Tunnels provide protection from bombing during aerial warfare.
• Tunnels avoid acquisition of costly land property.
• Tunnels provide protection against weathering actions like wind, rain, sun etc.
3.2 Disadvantages
• The initial cost of construction of a tunnel is high as compared to an open cut.
• Construction of tunnels requires long time in completing as compared to open cut.
• Specialized equipment and methods are required for execution of the work.
• It is necessary to have skilled labors and technical supervision of high order for
construction of the tunnels.

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Chapter 4
Classification of tunnels
1) On purpose
a) Traffic Purpose Tunnel
• Railway tunnels :- to carry Railway traffic.
• Highway tunnels :- tunnels used to carry roadway traffic
• Pedestrian tunnels: - tunnels used to cross pedestrian traffic.
• Navigation tunnels: - tunnels used to navigate from one point to another.
• Subway tunnels: - Tunnels constructed under the ground for public traffic.
b) Water Conduit Purpose :-
• Penstock for hydroelectric Power plant.
• Water Supply Tunnel.
• Sewer Tunnels.
2) On type of ground
• Tunneling in hard rock.
• Tunneling in soft rock.
• Tunneling in quick sand.
3) On the position and alignment.
i) Saddle or base tunnel.
• The tunnel that is constructed in between two valley’s in order to minimize the length of
tunnel such type of tunnel are called as saddle or base tunnel.
• During the design of saddled or base tunnel the important point is taken into
consideration is that the natural slope of valley should not be greater than the ruling
gradient of the road.

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ii) Spiral Tunnel
• In narrow valleys the additional length for minimum permissible radius is obtained by
forming a loop into the interior of mountain, such tunnel is called a spiral tunnel.
iii) Off –Spur Tunnels
• The tunnels that are made to short cut minor local obstacles such type of tunnels are
called as off – spur tunnel.
• The off- spur tunnels are very short in length
iv) Slope Tunnel
• To ensure the safe operation of steep mountains the slope tunnels are used.
• They are constructed from the economic point of view.
Fig – Spiral tunnel

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Chapter 5
Shapes of tunnels
1) Circular shape tunnel
• The circular shape tunnel is usually used for water and sewage conduit.
• These types of tunnels are best for resisting external or internal forces.
• It provides large cross- sectional area for least perimeter.
• It is usually used for non –cohesive soils.
• It is not advised for traffic tunnel because large filling is required for flat base.
• This shape is more difficult for placement of concrete lining.
2) D- Shape Tunnel
• It is the types of tunnel which has a roof as a segment of the circle whose sides are
vertical and floor is flat.
• D- Shape Tunnel is commonly used for sub- ways or the navigational purpose.
• The D-shape tunnels are usually used in hard rock.
• In D- shape tunnel the segmental arch roof transfers the load to the vertical straight
column support and then to the base.
3) Rectangular Shape Tunnel
• This type of tunnel which has a horizontal slab with the vertical supports.
• The BM and stresses exerted at the roof must be resisted by using steel girder to form
the roof lining.
• These tunnels are not used now a day’s .They are only used in the subways.
• These tunnels are usually constructed in hard rocks.
• Very difficult in lining.
4) Egg –Shaped Tunnel
• It is used for the sewer.
• Egg –shape of the tunnel provides a self-cleansing velocity to the water.

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5) Elliptical Shape Tunnel
• These tunnels are the type of the tunnels which are usually used to carry the fluid with
large viscosity.
• The elliptical Section with major axis vertical gives suitable section.
6) Horse –Shoe Tunnel
• This Shape tunnel consists of segmental roof with the inverts. The segmental roof and
the inverts resist the external pressure coming on them.
• They are suitable for soft rock.
• This shape is very commonly used for railway and highways in all countries.
7) Pilot Tunnel
• It is the type of tunnel whose diameter is less than the actual tunnel to be constructed
and is usually to connect the two tunnels which are constructed in a single mountain.
• Also used in emergency purpose.
• Also used to safeguard the equipment’s of the construction at the end of the day.

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Chapter 6
Tunneling in Hard Rock
6.1 Methods
1) Heading and Benching Method (top and bottom or up and down method)
• This method involves the driving of the top portion in advance of the bottom
portion.
• It is used when the tunnel section is very large and quality of rock is satisfactory.
• In this method the top heading excavation is usually 3 to 4 m ahead of the bench
excavation.
2) Drift Method
• Rock tunneling is sometimes carried out first in smaller section of the proposed
tunnel and then widened .This method is called as drift method.
• In drift method, the total c/s of tunnel is divided into n no. of square section .Each
section is about 2.5 to 3 m2 in area (face area).
• By converting the tunnel into small c/s part any part is selected for the excavation
which may be central part, top part, side part or bottom part.

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• And through this part the excavation is done from start to the end .Such excavation is
called as drift.
• The drift provides the ventilation or light during the excavation of the remaining part
of the tunnel.
3) Full face method :-
• In full face method, workers excavate the entire diameter of tunnel at the same time.
• In this method the mucking track could be placed progressively along with the
excavation.
• In this method tunneling is continuous.
• Full face method was limited to small tunnels only, but now with the improvements
and development in tunneling equipment more and more large tunnel can be driven
by this method.
• One of the machine which is usually used for cutting the full –face of the tunnel is
called as Tunnel Boring Machine.

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6.2 Tunnel Boring Machine
• The use of tunnel boring machine is on increasing way, because instead of drilling
and blasting this method can be used conveniently.
• In case of tunnel boring machine the rock damage is less, cut material is handled
systematically, safety of workers is great.
• The cost of tunnel lining is reduced and the operation is continuous with the help of
TBM.
• With the help of TBM ,the face area that can be cut is about 20 m2
• The diameter of TBM is up to 6m.
6.3 HARD ROCK TBMS:
• The Hard rock, either shielded or open-type TBMs are used to excavate rocks with
the help of disc cutters which are mounted on the cutter head.
• The rocks (muck) get chipped away as the disc cutter compresses stress fractures on
it.
• Now the excavated rocks are transferred to the belt conveyor through the cutter head
openings.
• These rocks are then run through multiple conveyors to get them removed from the
tunnel.

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6.4 Drilling, Blasting and hauling of muck
Before the invention of the TBM drilling and blasting was the only method of
excavating the material through hard rock.
For drilling and blasting we follow following steps.
• Small diameter drill is made with the help of different drilling equipment.
• The drill hole is clean for placing the explosive and packing of explosive with clay.
• Plantation of certain explosive material is done in the drill hole.
• Detonating the explosive.
• Fumes are released from the explosive.
• Final excavation or mucking of material is done.
6.5 Theory of drilling and blasting
• A drill hole normal to the face when exploded with proper charge will break out a gap
inclined at approximately 45 degree to the face.
• If two similar holes are kept side by side and fixed together they will blast a large
quantity of rock which will be about 2.25 times greater than the single faces.
• If three explosive with three similar holes are kept side by side and fixed together
than it will break 3.5 times greater than quantity of rock than that for single face.
• An inclined cut hole is more efficient than the hole that is drilled normal to the face.
Therefore, an inclined angle of 45 degree is made to the face of the rock and hole is
drilled .With the help of this inclined hole, the angle of crack also increases it the
about 54 degree 44 min to the axis of the hole.

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6.6 Drilling Equipment’s
• Drilling is the process of making holes using drilling equipment. The drilling
equipment varies w.r.t size of project, kind of rock, depth and size of hole, nature
of terrain, etc.
• The drilling equipment can be divided into two parts.
1) Percussion Drills
• A drill holes the drill bit and rotates it in partial manner/angle (90 or 120 degree) to
provide axial force for making a hole.
• Percussion drill breaks the rock by impact from the repeated blows.
• The popular varieties of percussion type of drills are

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a) Jack hammer
b) Tripod Drills
c) Stop Hammer
d) Drifter
e) Churn drills
f) Piston drills
g) Wagon drills
a) Jack Hammer
• It is the air operated percussion types of drill which is portable and hand operated.
• It is most used for drilling vertical holes.
• The weight of the jack hammer varies from 10- 40 kg.
• It can drill the hole up to 5 m depth.
• The impact blow action of the jack hammer is about 2200 blows/min.
b) Tripod Drills
• This are similar to the jack hammer, expect that it is mounted on tripod to provide
sufficient stability.
• Tripods are usually very low and require drill changes every 1m or so.
• They are not much in use except for very hard rock.

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c) Stop Hammers
• This is modification of jack hammer which are mounted on certain vehicle to hold
the drill against the work and are usually used for up holes.
d) Drifters
• The drifter is an air operated precaution type of drill similar to the jack hammer but
is so large that it needs mechanically mounting.
• They are used for drilling down ,horizontal or up holes
• They can drill up to of 12 cm diameter holes.
e) Churn Drills ( Well drills )
• They are also called are well drills.
• Churn drill can drill hole up to 15 cm diameter.
• Churn Drill can drill at any angle and has the penetrating depth up to 100 m.
• They are operated by steam or gasoline.
f) Piston Drill
• The piston drill is securely fastened and traveled the full length of the piston
stroke.
• It can drill a hole of 6 cm in diameter and can drill a hole up to 10 to 20 m long.
• The impact blowing action is about 200 blows per minute.

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g) Wagon drill
• The wagon drill is the drifter mounted on a vehicle to provide portability in drilling
the holes.
• They are used extensively to drill the holes up to 12 cm in diameter and up to 10 m
in depth.
• Their performance is better than jack hammer.
• They can be used to drill the hole at any angle from down to up.
2) Abrasion drill
• The abrasion drill is a type of drill which grinds the rock up to small particles
through abrasion effect of bit that rotates in the hole.
• The common examples of abrasion drill are
a) Blast hole drills
b) Short drills
c) Diamond drills
a) Blast hole drill :-
• This is the type of rotary drill which works on the system of compressed air and
disintegrates the rock as it rotates over it.
• The type of abrasion drill is used for drilling the hole up to 100 m in depth.

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b) Short drills
• This is the rotary abrasion type of drill which has the rough surface at the bottom
and makes the hole in certain rock by crushing it.
• Short drill can drill a hole up to 75 in diameter and up to depth of 200 m.
c) Diamond drill
• Diamond drill is a rotary abrasion types of drills whose bit consists of metal matrix
in which they are embedded a large number of diamonds.
• Diamond drills are uneconomical, hence are used in less quantity.
6.7 Blasting
• The blasting is the operation performs to loose the rock so that it can be excavated
or removed from its existing position.
• Blasting is accomplished by discharging an explosive that has been placed in a
hole specifically drill for this purpose.
• During the blasting operation the drilled holes are made and cleaned, the charge of
explosive is placed at the bottom of blast hole or drill holes; remaining portion of
the hole is filled with the clay and tampered.
• The size of the explosive ranges from 2.5 to 20 cm in diameter and its length is
about 20-60 cm and tampered.
6.8 Types of Explosive
a) Straight Dynamite
• It is the first type of explosive with which all high explosives are compared for
strength.
• Its primary constituent is nitro- glycerin varying from 15-60%

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• They are highly water resistance and a desirable property for sub- marine blasting.
• Because of bad fumes they have been replaced by other types.
b) Ammonia Dynamite
• It contains equal parts of nitro- glycerin and nitrate of ammonia as the explosive
material.
• They come in the strength of 15-40%, but are not so sensitive as straight
dynamites.
• They are suitable for soft rock and fairly water resistance and their fumes are not
so bad.
c) Gelatin Dynamites
• They are of two types
 Straight Gelatin dynamites
 Extra or special Gelatin dynamites
• Both this type of gelatin dynamites consists of jelly of nitroglycerin and nitro-
cotton.

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• In extra or special gelatin, part of nitro-glycerin is replaced by nitrate of ammonia.
• Both these types are highly water resistance and their fumes are good.
• Their jelly like plastic consistency permits solid loading in a hole.
• They are quick and have high shattering effect.
• Because of these characteristics they are chosen for most rock tunneling work.
d) Semi –Gelatin Dynamite
• In a recent development, consisting principally the complex compound of nitrate
of ammonia with same gelatin, nitro- glycerin, nitro – cotton, semi –gelatin is
formed.
• Semi- gelatins are bulkier than the straight or extra gelatin.
• They are water resistant and fume quality is good.
• Because of their low density, they are cheaper than extra or gelatin dynamite used
in soft rock and lime –stone work.
e) Blasting Gelatin
• Blasting Gelatin are also a recent, fast, strong explosive.
• They have the consistency same like soft rubber and it is fully water proof.
• It is adaptable for wet work.
• Its fumes are extremely bad and its strength is about 100%

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f) Other High Explosives
• Several Special high explosives are made, developed for special condition
especially for disintegration of hard rock.
• Some of the other explosive are
• TNT – Tri –Nitro- Toluene
• RDX –Rapid detorating explosive
• Pent – Penta Eny thital

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Chapter 7
Case Study on Maroshi - Ruparel water tunnel Mumbai
7.1 Introduction
• Mumbai’s water network is crumbling under the strain. Its mains system is at least 80
years old, the majority of it laid in the colonial era. Though the city has seen some
water distribution projects post-independence, they were still more than 60 years old.
• Much of the system works through surface pipelines, which are prone to leakages and
theft. This highly pressurized network is further hindered by passage under slum land,
which adds even more complication to their maintenance. Likewise, Mumbai’s main
water line runs beneath the runway of Mumbai international airport, making it doubly
difficult to maintain, while a major burst could affect the movement of air traffic into
and out of the city.
• Hindustan Construction Company (HCC) was awarded the Contract of Maroshi-
Ruparel College Tunnel Project by the Municipal Corporation of Mumbai in
September 2007 with a Contract value of Rs 415.10 crore. This is a Water Supply
Project executed under Jawaharlal Nehru National Urban Renewal Mission
(JNNURM) and is funded by the Government of India, Government of Maharashtra &
Municipal Corporation of Greater Mumbai.
• The tunnel stretch is divided into three sections namely, Maroshi-Vakola (5.83 km
long), Vakola-Mahim (4.55 km long) and Mahim-Ruparel College (1.86 km long).
Maroshi-Vakola tunnel stretch is the longest section of the Maroshi to Ruparel College
water tunnel.
• The Maroshi-Ruparel tunnel work consists of construction of tunnel having 3.60 m
diameter and 12.24 km long using Tunnel Boring Machine from Maroshi connecting
to Ruparel College. The tunnel is connected with Shafts at Maroshi, Vakola and
Mahim. The shafts are 12 m in diameter and about 80.00 m deep equivalent to a to 26-

30. 30
storey building deep into the ground. It will be through these shafts that localities will
get water supply.
• The BMC began the underground tunnel project to stop leakage and water thefts from
the water pipelines .The other focus of the project is to replace the water pipelines that
are centuries old and have corroded at several spots ,causing sewage water to mix with
drinking water.
• The Vakola-Mahim section passes below the Mahim creek while the Maroshi-Vakola
section crosses both of Mumbai airport’s runways at around 70 meters below ground
level. The tunneling work was carried out without disturbing any operations on the
ground level.

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• The tunnel boring was extremely challenging due to heavy seepages and varying rock
strata. During monsoon, the tunnel seepage had increased to about 25,000 m3 per day.
Extensive grouting was carried out to control the same.
7.2 PROCESS
First, a shaft with a diameter of 10 meters was constructed at a depth of between 70
and 80 meters. This served so that contractors could deliver all the necessary plant,
machinery and equipment, including tunnel boring machines (TBMs), locomotives,
water pumps and concrete mixers, through it to reach the 70-metre depth required for
the boring and drilling.
This was done by the gripping of jacks and alignment of TBM cutter heads for boring
at a width of 3.6 meters through the earth.
The concrete lining is cast on site rather than being pre-cast elsewhere. Once a stretch
of boring is complete, an epoxy-coated reinforcement layer is fixed into place; the
shutters and bulkheads are then set to pour ready-mix concrete using the agitator cars.

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7.3 Conclusion
• After completion, the tunnel improved the water situation in south and central Mumbai
by supplying 1,100 million liters daily. The tunnel replaced the old upper Vaitarna and
Vaitarna mains in this section. It improved the water supply to Vakola, Mahim, Dadar
and Malabar Hill significantly.
• This project is part of the rehabilitation and improvement of the drinking water
conveyance / distribution system from Bhandup Treatment Works to Western Suburbs
and Southwest part of the Mumbai city.
• BMC town planners expect the new tunnel to have a number of advantages over the
existing surface pipeline, because it travels at such great depth, meaning that the structure
cannot be tampered with, as is the case with surface pipelines. In addition, there are fewer
chances of leakages and water theft, and most importantly, the tunnel is not expected to
require major maintenance over the next 100 years. And since the entire distribution
system is made of concrete, it will not corrode, invariably happens with surface pipelines.
• The project is also designed to withstand earthquakes.

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References
a) Harbor Dock and Tunnel Engineering Textbook by R srinivasa.
b) Textbook of Tunnel Engineering by S.C.Saxena
c) Textbook of Tunnel Engineering by Rangwala
d) www.google.com
e) Performance characteristics of tunnel boring machine in basalt and pyroclastic
rocks of Deccan traps –Research paper by Prasnna Jain, A.K. Naithani, T.N.
Singh.