International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 8 – Jul 2014
Case Study on Design and Construction of Tunnel
M.S.Rahul
Undergraduate Scholar, Hyderabad
Abstract —A tunnel may be for foot or vehicular road traffic, for
rail traffic, or for irrigation purposes. Some tunnels are aqueducts
to supply water for consumption or for hydroelectric stations or
sewers. Utility tunnels are used for routing steam, chilled water,
and electrical power. The tunnel is relatively long and narrow; in
general the length is more than twice the diameter The Dr. B.R.
Ambedkar Pranahitha Chevella Sujala Sravanthi Lift Irrigation
scheme’s objective is to irrigate 16.40 Lakh Acres of command area
in the drought prone areas of Telangana region viz., Adilabad,
Karimnagar, Medak, Nalgonda, Nizambad, Warangal and Ranga
Reddy districts of Telangana state. The scheme envisages
construction of barrage across Pranahitha River, a major tributary
of Godavari River at Tummidihetti (V) in Koutla (M) of Adilabad
district and 160 TMC of water from Pranahitha River is proposed
to be diverted to Sripada Yellampally Project from where it is
carried to command areas through lift irrigation schemes, gravity
canals, tunnels, Modernization of tanks and reservoirs for
irrigation total Ayacut of 16.40 Lakh Acres and providing drinking
water facility to villages and also providing required water to
industries.
Keywords— Tunnel, Investigation, Excavation, Drilling, Portals,
seepage control, Grouting, Measures
Canal to existing Flood Flow canal to feed Mid Mannair
Reservoir with the components such as Lined Gravity canal, CM
& CD works, lifts, pressure mains and lined tunnels with all
associate civil, Hydro Mechanical & Electro Mechanical works
was
entrusted
to
“MEIL-SEW-MAYTAS-BHEL
(CONSORTIUM)”,
II. Scope of Work
The package starts from Kakatiya Canal @D-83 in Ragampet
(V) to existing Flood Flow canal near Shanagar (V).
a. Site investigation report(s).
b. Brief review of Geological and Geotechnical
investigation.
c. Approach by Adit tunnel 8 m dia D-Shaped and 1.609
km in length with 1 in 12 slope
d. Twin tunnel from the Kakatiya canal @D-83 in
Ragampet (V) to surge pool at lakshmipuram (v) for
about 4.133 km with 10.0 m dia and 7.5 m dia.
e. Underground Surge pool 350 x 20 x 56 m D-shaped.
f. Underground Pump house 205 x 25x64 Mts with a lift of
about 109.10 Mts
g. Delivery cistern
h. The length of Gravity Canal is 4.060 Km from delivery
cistern to Mothevagu reservoir.
i. Foreshore of Mothevagu reservoir to Flood Flow Canal
length of link canal is 1.900 Km
I.
Introduction
The Dr.B.R.Ambedkar Pranahitha Chevella Sujala Sravanthi
Lift Irrigation Scheme (Dr.BRAPCSSLIS) is being constructed
having the 22 lifts. The project envisages irrigation of about
16,40,000 acres of uplands in the six districts and the total lift
height from the river Pranahitha at RL+150.00m to Chevella
reservoir at RL+635.00m, i.e., 493M These are carried out by III.
multiple stages lifting and conveying through tunnels and
gravity canals. The total length of system is divided into two
parts, length of Gravity canal and length of the Tunnel. Length
of the Gravity canal is 849 km (approx.) and Length of the
Tunnel is 206 km (approx.). The total number of lifts is 22. The
total power required for this lift is 3375 MW; estimated time for
completion is 48 Months. The entire project is divided into
several packages to facilitate execution of the work
simultaneously. There are 28 packages under this project. In this
study, analysis is done on Dr.B.R.Ambedkar PranahithaChevella Sujala Sravanthi package 8. The work of “Pranahitha
Chevella Sujala Sravanthi lift irrigation scheme-link-II-package08” detailed investigation, designs and execution of lift
irrigation scheme for drawl and lifting of 114.24 TMC of water
from Ragampet
(v), near Kakatiya canal, Choppadandi (M), Karimnagar District
to Mothevagu Reservoir and carrying by a gravity
ISSN: 2231-5381
Site Investigation
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 8 – Jul 2014
IV.
Geological and Geotechnical Investigation
Design and construction of tunnels in rock require thought
processes and procedures that are in many ways different from
other design and construction projects, because the principal
construction material is the rock mass itself rather than an
engineered material. Uncertainties persist in the properties of the
rock materials and in the way the rock mass and the ground
water will behave. All these uncertainties must be overcome by
sound –flexible design and redundancies and safeguards during
construction. The design of tunnels must involve selection or
anticipation of method of construction. Geology plays a
dominant role in many major decisions made in designing and
construction of a t unn el. In tunnels, unlike other structures, the
ground acts not only for the loading mechanism, but as t h e
primary supporting medium as w e l l . When the excavation is
made, the strength of the ground keeps the excavated hole open
until the supports are i n s t a l l e d . Even after supports are in
place, the ground pr ovi des a substantial percentage of the
load-carrying capacity. Thus, for a tunnel, the rock or soil
surrounding a tunnel is a construction material. Its engineering
characteristics are as important as those of the concrete or steel
used into the aspects of the work.
A. Seismicity
According to GSHAP the state of Telangana falls in a region
with low 10 moderate seismic hazards. As per the 2002 Bureau
of Indian Standards (BIS) map, this state also falls in zones II
and III. Historically, parts of this have experienced seismic
activity in the M 5.0-6.0 range. The Godavari river valley,
adjustment to the site is within the NW-SE trending faults.
These faults still show moderate seismicity occasionally. The
Godavari graven area is in seismic zone II. In this zone an
earthquake of magnitude of 6 or intensity VIII may be expected.
The earthquake of magnitude 5.3 was measured at
Bhadrachalam in 1969.
As per IS-4880 (part-V), the tunnel lining is not designed foe
seismic force unless the tunnel crosses an active fault. In which
case, some flexibility is provided at that section to all for some
movement in case of earthquake. However, at locations where
studies in indicate that seismic forces will be significant they
shall be catered for in the design.
B. Field Work
The site of package-8 is located in Karimnagar district of
Telangana state. Six boreholes were drilled in the alignment of
the proposed tunnel, varying depth of 100.0 m to 130.0 m. The
subsurface investigation is carried out by boreholes and electroresistivity method (ERM) for suitability of the proposed site for
the construction of tunnel.
C. Electric Restivity Method (ERM)
Resistivity surveys have been conducted along the alignment of
tunnel for 4.133 KM of the package-8, to assess the sub –surface
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soil classification, which facilitate to design of various
components of the tunnel, strata expected to encounter during
the excavation etc.
D. Vertical Electrical Sounding (VES)
VES is conducted along the alignment axis at 100m intervals.
The interpreted data of the VES gives various sub-surface layer
thickness, its nature and depth to the massive rock.
V.Tunnel Design
The layout of tunnels depend on the grade, clearance required,
alignment etc. wherever possible, from the standpoint of general
alignment and cost, tunnel alignment should be straight to
facilitate construction. Curved tunnels have been used on many
railroad, water conveying tunnels, and highways, particularly in
mountainous areas. As per the geological report made available,
the entire stretch of tunnel from Km. 0.0 to Km. 4.133 passes
through grey and pink granites rock strata.
The total length of the tunnel is approximately 4133m due to
length of tunnel (4.133 Km), and the entry exit of the tunnel
cannot be approached without shafts or construction of Adit, it is
necessary to establish a construction adit to provide two working
faces in each tunnel to complete the work in the schedule period.
A. Geometry of the Tunnel
Methods and sequence of excavation affect the loads and
displacements, which must be resisted by initial and permanent
ground supports. The basic shape of an excavated opening must
be selected for practicality of construction. IS 4880 part II 1976,
lays down general guidance in regard to shape of the various
sections generally use in tunnels. However, the said IS code has
left the choice of particular shape on designer’s judgment based
on prevailing conditions at site. The first step in the design of a
tunnel is the determination of the cross section required for the
trouble free operation.
These selections of the tunnel cross-section influenced by:
o The clearances specified in view of the vehicles and
materials transported in the tunnel,
o Geological conditions,
o The method of driving the tunnel and the materials
strength of tunneling.
D-SHAPED tunnels are best suited in ‘conventional drilling and
blasting method of construction point of view in good rock
strata, as they have flater invert. In Pranahitha-Chevella lift
irrigation scheme Package-8, tunnel is proposed with a 10.3m
diameter D-Shaped Tunnel in right tube and 7.75m D-shaped
tunnel in left tube. The hydraulic loss due to the D-shape tunnel
is negligible in this case, compare with a circular tunnel of same
cross sectional area, hence we can use D-shaped tunnel as
mentioned above without losing any advantage of circular
tunnel.
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
B. Shotcrete and Rock Bolt Initial
As the tunnels generally passes through different types of rock
formations, it is necessary to work out alternative cross sections
if the tunnel depicting other acceptable types of support systems.
The shotcrete in combination with rockbolt and wire mesh
provide a good and fast solution for both initial and permanent
rock supports. Being ductile it can absorb considerable
deformation before failure
VI.
Construction
The basic components of underground construction include the
following:
 Excavation, by blasting or by mechanical means.
 Initial ground support.
 Final ground support.
Other important components of construction include the
following:
 Site preparation.
 Surveying.
 Portal preparation
 Ventilation of the underground works
 Drainage and water control
 Hazard prevention
 Controlling environment effects etc.



D. Precision Survey
The precision survey and setting out of the tunnel alignment
shall consist of transferring the obligatory points like portal
points, shaft/adit location, etc., from topographical
maps/detailed design drawings to the actual site of construction.
This is done either by “Direct Setting Out” or by
“Triangulation”. In the mountainous regions it is extremely rare
possibility that both the ends of the tunnel will be visible from
each other and hence “Triangulation has to be invariably
adopted for setting out the alignment. The levels of the various
portals along the tunnel are fixed accurately by means of Total
Station or using “Reciprocal Leveling”.
E. Methods of Underground Excavation
A. Sequence of Excavation For Tunnel
The excavation and portal of the adit tunnel is established first.
Main tunnel excavation for left tube and right tube is carried out
through the adit tunnel from both face in each tunnel
simultaneously by full face or heading and benching method
depending upon the strata encountering and the machines using
at site. The design team should specify or approve the proposed
method of excavation. This tunnel is proposed to excavate using
conventional drill and blast method
B. General Procedure of Underground Excavation
Tunnels can be driven through almost any material in nature, but
the methods used and costs differ radically. Thus, the method
used in tunneling in earth, soft sediments or crushed weathered
rock depends chiefly on the bridge action period of the material
above the roof of the tunnel and the position of water table,
whereas the method used for tunneling through hard, intact rock
requiring little or no supports depends upon the strength and
condition of rock, because of great longitudinal extent of the
work, many different kinds of conditions are encountered, which
for maximum economy should be excavated and supported
differently.
C. Preliminary Works
The preliminary works required commencing the excavation of a
tunnel consists of the following:
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
Precision Survey and setting out of the tunnel
alignment. Open excavation for portal or excavation for
shaft.
Arrangement for collection of surface water and its
drainage by gravity flow or pumping.
Access roads to mucking areas.
Erecting or winching and hauling equipment.
Establishments of field workshop, compressors and air
lines, pumps, water lines, ventilation fans and ducts,
lighting, concreting arrangements, supports erection
arrangements, etc.
The underground excavation for tunnels shall be carried out in
conformity with IS: 5878 Part II / Section-1 or other relevant
reference mentioned as per the tender documents Tunneling soft
strata shall conform to IS: 5878 part III other relevant references
mentioned as per the tender documents. The actual operations
for underground excavations may vary with the type and size of
tunnel, method of excavation, type of geological formation
encountered, equipment available, and the overall economics.
Following are the methods commonly adopted for excavation of
tunnel.
1. Full and Partial Face Advance
Most tunnels are advanced using full-face excavation. The entire
tunnel face is drilled and blasted in one round. Blast holes are
usually drilled to a depth somewhat shorter than the dimension
of the opening, and the blast “pulls” a round a little shorter than
the length of the blast holes. The depth pulled by typical rounds
is 2 to 4 m in depth. Partial face blasting is sometimes more
practical or may be required by ground conditions or equipment
limitations.
2. Full Face Attack
In this method, the entire cross-section area of the tunnel to be
excavated is attacked simultaneously. This method is generally
recommended for small size tunnels in good rock conditions
where major rock falls are not anticipated.
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3. Top Heading And Benching
This is the most common method, where the top part of the
tunnel is blasted first, at full width, followed by blasting of the
remaining bench. The bench can be excavated using horizontal
holes or using vertical holes similar to quarry blasting.
4. Drift Method
In driving large tunnel or tunnel in very poor strata it may be
economical to drive a small tunnel called drift or a pilot tunnel
prior to excavating the full face. Depending upon the nature of
rock and other parameters, a drift may be excavated in the
center, side, bottom or top.
In this package 8, Top Heading and Benching method is adopted
for underground tunnel excavation.
The other methods used are:
1.
2.
3.
Cut and cover methods
Mechanized means such as Tunnel Boring
Machines or Continuous miners
Tunneling with aid of a protective shield.
Drilling, Charging and Priming Patterns
Blasting Design
An important step in tunnels is Blasting. Blast design that will
produce desired rock fragmentation results and low vibration
levels. They specify explosive quantities and design borehole
drill patterns including size, depth, and spacing. These factors
vary based on the geology and location of the blast site.
Different rock types require different kinds or amounts of
explosives and different borehole spacing. Blasts are also
designed to produce fragmentation, or rock size.
Trial Blast
As per the geological report, this tunnel passes through sound
granite strata. Hence in this tunnel, it is proposed to execute
adopting ‘conventional drilling and blasting method’ with
drilling boomers. Since the size of the tunnel is more than 8m it
is proposed to execute the tunnel by heading and benching due
to the bigger size of the tunnel. If any fracture zone encountered
during the execution of the project, it is proposed to execute the
same by heading and benching with rock supports.
F. Marking of Tunnel Profile
The center of the tunnel and its level is marked on the face of
the tunnel with the help of the precision survey instrument
before each blast and from that center line point the designed
shape of the tunnel is marked on the face.
G. Setting up and Drilling Holes
The blast patterns shall include the following:
- Drilling patterns
- Charging patterns
- Priming Pattern
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Trial blasting will be performed at the beginning of the works in
order to optimize blast design and drilling patterns. The
purposed of this trial blasts is as follows:



Estimation of blast design parameters suitable to the
site
Suitability evaluation of the approved blast design.
Checking the blast vibration level.
H. Loading Explosives and Blasting
Explosives used in blasting are generally of emulsions type
made of varying percentage of strength. Before loading is
started, each hole is blown with high-pressure air jet or with
water. A primer cartridge containing the detonator pointing
towards the bottom of the hole and is tamped well into the
bottom with the help of wooden or plastic pole. Finally, the
remainder of the hole is filled with inert material (like damp
mixture of sand and clay) and tightly clamped. The holes are
then blasted from the safe distance. Adequate safety precautions
are taken during drilling and blasting operations in conformity
with IS: 4081 and other relevant guidelines.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 8 – Jul 2014
or suitable attachment. Manual scaling may not be advisable or
practical in safety point of view.
L. Removal of the Muck
I. De-Fuming or Removal of Foul Gases by Ventilation
Ventilation is an important aspect, which has to be duly taken
care of for efficient underground excavation of the tunnel.
Adequate ventilation must be provided to make the working
space safe for workers, by keeping the air fresh and breathable,
free from harmful obnoxious gases and dust. Minimum
requirements of purity of air, dust control and volume of air are
in accordance with IS: 4756.
The tunnel can be ventilated either by blowing air in or
exhausting it out through a duct. In the blowing mode, fresh air
enters from the surface through a vent pipe to a point near the
face. This mode has advantage of constantly supplying fresh air
to work space. In exhaust mode, the foul air is exhausted
through the vent line. While this method creates a better
environment along the tunnel, any heat, moisture, dust and
smoke generated along the tunnel is delivered to the vicinity of
the face.
Dumper
VII. Initial Ground Reinforcement (Rock Bolts)
Initial ground reinforcement consists of; Un-tensioned rock
dowels and occasionally, tensioned rock bolts. These are
referred to as ground reinforcement, because their function is to
help the rock mass support itself and mobilize the inherent
strength of the rock as opposed to supporting the full load of the
rock. It is much more economical to reinforce the rock mass
than to support it. Rock bolt is the general term that includes
rock dowels and cable tendons. Specifically, bolts are pre
tensioned, while dowels are initially unstressed. The installation
process is simple: drill the hole insert the requisite number of
cartridges insert the steel bar with a spinning action and continue
spinning for about 60 seconds to ensure complete mixing.
Ventilation ducts.
J.
The material removed as a result of blasting is loaded into
dumpers or mine cars, as the case may, and is taken out of the
tunnel. In principle, tire or crawler mounted loaders/excavators
and suitable dumpers are used for mucking operation. Removal
of muck from underground excavations shall be in conformity
with IS: 5878 Part – II/Section-2 and other tender provisions.
The excavated materials (rock, soil etc.) from the tunnel shall be
transported to the specified dumping area. A haul road of slope
not greater than 1 in 10 shall be constructed for the hauling of
excavated muck.
Checking Misfires
Immediately after the tunnel has been de-fumed and ventilated,
the blasted face is checked carefully for any misfires. For this,
an experienced and competent Forman enters the tunnel,
removes the loose rock carefully from the face and makes sure
that all cartridges have been fired.
K. Scaling The Loose Material
In these tunnels the rock bolts considered most appropriate are
reinforcing steel bars, typically 25 mm diameter, 12 tons proven
capacity. For 25 mm passive bolts, holes of 32 mm to 38 mm are
required. The hole is filled from the bottom with cement
capsules and the bolt is inserted as per the designs. Care must be
taken to ensure that the hole is filled up to full depth. The bolts
are threaded outside. When the grout is set, a washer plate is
placed against the rock and secured in position with a nut. When
shotcrete is used, the washer should be outside the main layer of
shotcrete.
After the checking of the misfire is over, the scaling operation
will be carried out by use of excavators with hydraulic hammer
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DRILLING FOR ROCK BOLTS
SURFACE PREPARATION
Good adhesion to the ground with the initial layer and good
bond between successive layers are prerequisites of good
shotcrete. This can best be accomplished with a high-pressure
combination air-water jet applied with a long jet pipe nozzle
held relatively close to the surface.
ROCK BOLTS
VIII.
Seepage control
A. Dry-Mix Aggregate Preparation
The process of Tunneling is always disrupted with the presence
of Ground water table in its path and also the local seepage of
water. This is taken care by the use of Shotcrete and drilling
Ground water drainage holes
IX. Shotcrete
When dry-mix aggregate storage is on-site, protection from the
elements is necessary. Stock piling by size groups should
prevent sub size segregation. For best result, an aggregate
dampness of 3% to 6% should be maintained. Less will absorb
too much mix water; more will result in too high water cement
ratio.
Shotcrete today plays a vital role in most of the tunnel and shaft
construction in rock because of its versatility, adaptability and
economy. Desirable characteristics of shotcrete include its
ability to be applied immediately to freshly excavated rock
surfaces and to complex shapes such as shaft and tunnel
intersections, enlargements, crossovers and bifurcations and the
ability to have applied thickness and mix formulation varied to
suit variations in ground behavior.
B. The Mix
The mix design shall be as per the IS standards. The mixing of
materials shall be done using a suitable capacity batching plant.
Inclusion of steel fibers will require little or no change from the
plain shotcrete mix. The principle effect will be increased. Over
all, the mix design should keep water cement ratio and the
cement factor as low as possible and the coarse aggregate
fraction as large as practicable.
Shotcrete is not just “pneumatically applied concrete”. Although
the basic materials (cement, aggregate, water) are the same and
meet the same Indian Standards, additives (e.g.: accelerators,
micro silica and steel fibers) change its character to make
shotcrete unique and usable in quite a different fashion than
concrete.
In this package 8, Wet mix procedure has been adopted. The wet
mix process consists of mixing measured quantities of
aggregates, cement, and water and introducing the resulting mix
into a vessel for discharge pneumatically or mechanically
through a hose to final delivery from a nozzle. It has the
advantage of rigidly controlling the water/cement ratio of the
product. Existing equipment can handle maximum aggregate
size of 3/4 inches.
C. Nozzle
The best shotcrete “on the wall” is produced when the nozzle is
kept within 3 to 5 feet of the surface being shot and
perpendicular to the surface or within 15 degrees of the same.
Deviation from this will result in less compaction and more
rebound. Considering the particles in shotcrete stream is
travelling at 170 to 340 mph. In package 8, a remotely controlled
nozzle at the end of a long bottom has been adopted.
D. Curing
Curing of the shotcrete shall be taken up by spraying water jet
on the surface.
X. Backfill Concrete
On tunnel supports and tunnel lining respectively, the job of the
tunnel support or tunnel lining does not end with the
installations of a support system (steel ribs, rock bolts, shotcrete)
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 8 – Jul 2014
and provision of lining. It is necessary to backfill the space
between the support system and the excavated surface, for
arresting the displacements and movement of the strata around
an excavated and supported system and the excavated surface.
The back filling is done by means of placing tightly packed M20
concrete behind the supports.
XI. Grouting
In order to ensure complete of concrete lining and the rock
behind it, contact grouting with cement grout will be done after
the lining concrete has matured for at least twenty-one days (21).
Grouting in tunnels is of two types:
XII.
Tunnel Lining
The lining of the tunnel will be taken up when the excavation of
the tunnel, has been completed. Keeping in view that three faces
are available for concreting it is proposed to use three
conveniently designed shutters for lining of the tunnel to
complete the lining as per the Construction Schedule. In the
sections, where excavations of benching of tunnel are
completed, shall be concreted with the help of specially
designed shutters for overt and sidewall. The shutters will be
10.5 to 12.5 meter long, which will enable the concrete lining of
whole overt section of 10 to 12 meter length in one go. These
shutters give an average lining progress of 150
meter/month/shutter.
A. Back fill or contact grouting
B. Pressure grouting or consolidation grouting
A. Contact Grouting The main purpose of contact grouting
is that it fills up all voids and cavities between the
concrete lining and the rock. Contact grouting also
known as low pressure grouting or back fill grouting.
Back fill grouting shall be done at a pressure not
exceeding 5 kg/cm2 and shall be considered as a part of
concreting. The normal varies from 2 kg/cm2 to
5kg/cm2. It shall be done throughout the length of the
concrete lining not earlier than 21 days after placement
after the concrete in the lining has cooled off.
B. Pressure Grouting or Consolidation Grouting
In the conventional drilling and blasting method of tunnel
excavation and blasting method of tunnel excavation, the rock
around the cavity gets shattered to a certain depth depending
upon the depth of blast holes and type of rock. The aim of
consolidation grouting is to consolidate the shattered rock by
filling up the joints and discontinuities in the rock, which got
opened out during blasting operations. As a result of pressure
grouting, the rock quality gets improved thus increasing the
resistance of the rock to carry internal water passage. The
consolidation grouting is done after back fill grouting is
completed in a length of at least 60 m ahead of the point of
grouting. Pressure grouting shall be done all around the cavity
and for a uniform radial distance equal to least 0.75 times the
finished diameter of tunnel from the finished concrete face. The
normal range of pressure grouting shall be 7 to 10 kg/cm 2.
Process of Grouting
Drilling
holes
Cleaning
and
washing
holes
Testing
holes
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Grouting
holes
Testing of
grouted
zone for
efficancy
of
grouting
Tunnel Lining
A concrete pump of 30 cum capacity or equivalent shall
accomplish the Placements of concrete behind the shutter. The
concrete shall be produced by suitable capacity concrete batch
plant installed at the entrance and adit of the tunnel.
XIII.
Ground Water Drainage Holes
As per IS: 4880 (Part V)-1972 drainage holes may often provide
in other than water conveying tunnels to relieve external
pressure, if any, caused by seepage along the outside of the
tunnel lining. It is recommended that drainage holes may be
spaced at 3m centers, at intermediate locations between the
grout rings. At successive sections, one vertical hole may be
drilled near the crown alternating with two drilled holes, one in
each side wall. Drainage holes extend to a minimum of 15cm
beyond the back of the lining or grouted zone. Since this is a
water-conveying tunnel and the ground water table is below the
tunnel bed level, it is proposed not to provide any water drainage
hole
XIV.
Safety Measures
Safety is of utmost importance during the construction of
tunnels. Provision of Helmets, Masks and Work wear is
mandatory for the work force
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REFERENCES
Code Books
o
IS 4880:1972
Part I General design
Part II Geometric design
Part III Hydraulic design
Part IV Structural design of concrete lining in rock
Part V
soils
Structural design of concrete lining in soft strata and
o
XV.
Conclusion
The tunnel carries water from Pranahitha-Chevella Tank through
tunnels. This enables us to lift water from lower region to higher
region through hydraulic pumps and drop the water in gravity
canals from which the water is distributed to the irrigated lands.
Our project is Study of the construction of tunnels that are a subpart of the PCLIS, which is package-8 situated at Laxmipur,
RamaduguMandal. The use of tunnel irrigation reduces the need
of LAND ACQISTION, which usually takes up most of the
allotted budget to the project. The tunnels also have a low
Operation and Maintenance of them. It is both effective and
economical with use of Tunnel system.
Part I
The project has Twin D-shaped tunnels of diameter more than
10.0m; in such case a pilot tunnel is excavated first followed by
slashing on both the sides of the pilot tunnel.
Part V
A. Concrete Lining is provided depending upon the rock
class encountered during the excavation, in the
following way:
Part II
IS 5878:1971
Precision survey and setting out
Underground excavation in rock
Section I: Drilling and blasting.
Section II: Ventilation, lighting, mucking and
dewatering.
 Section III: Tunneling method for steeply inclined
tunnels, shafts and underground powerhouses.


Part III Underground excavation in soft strata
Part IV Tunnel supports


Concrete lining
Introduction to Tunnel Construction
By David Chapman, Nicole Metje, Alfred Stärk
Design of Reinforced Concrete Structures
By S.Ramamrutham.
Class I- No rock supports are required, but as per agreement
provisions 500mm M20 plain cement concrete lining is
provided.
Class II- No support is required except spot bolt at some points
and also as per agreement 500mm M20 plain cement concrete
lining is provided.
Class III- Initial rock support shall take the entire load and there
is no need of final concrete lining. As per agreement 500mm
M20 plain cement concrete lining is provided.
Class IV- Initial ground support shall be provided with 50mm
thick shotcrete immediately after excavation with steel supports,
lagging, backfill concrete and grouting.
Class V- Initial ground support shall be provided with 100mm
thick shotcrete immediately after excavation with steel supports,
lagging, backfill concrete and grouting.
ISSN: 2231-5381
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