A ppt About a method that is very useful in tunnel construction

1. BY :- SUMIT
MANDLA
A presentation about
Under The Guidance of:
ER.
ASSISTANT PROFESSOR
Department of Civil Engineering in
KITE, Jaipur
( 13EKTCE453 )
NATM

2.  It is an underground or underwater
passageway, dug through the surrounding
soil/earth/rock
 Tunnels are underground passages used for
transportation. They could be used for carrying
freights and passengers, water, sewage, etc.
 A tunnel may be for foot or vehicular road
traffic, for rail traffic, or for a canal.

3. REASONS TO BUILD A
TUNNEL
 When the lane encounters an obstacle such as a
mountain to avoid bypassing the obstacle
 Built sometimes to overcome a water obstacle as
a replacement for building a bridge above it.
 Built to connect between military posts so the
movement between them will not be visible for the
enemy
 Sometimes built for infrastructure like electricity
cables, water, communication and sewerage to
avoid damage and disruption above ground

4.  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
 If tunnels are provided with easy gradients, the cost is
decreased
 In case of aerial warfare and bombing of cities, the
tunnels would grant better protection as compared to
bridges

5. (A)CIRCULAR :
 For carrying water and sewerage circulation shape
tunnels are used .ex. Aqueduct
 Circular tunnel are not prefer as traffic tunnel.
(B) EGG – SHAPED SECTION :
 These section have narrow cross sections at
bottom. They are best suited for carrying
sewage.
 They maintain self-cleansing velocity of flow
of sewage both in dry and rainy seasons .

6.  These tunnels serve as water sewage
condition. They are difficult construct .
 They cannot be used as traffic tunnels
because of their narrow base
(C) ELIPTICAL SECTION
(D) HORSE SHOIE SECTION
 This form consists of a semi-circular roof together
with arched sides and a curved invert.
 They are most popular as traffic tunnels for road
and railway routes .

7. TUNNELING METHODS
 DEPEND ON :-
 ground conditions,
 the ground water conditions,
 the length and diameter of the tunnel drive,
 the depth of the tunnel,
 the logistics of supporting the tunnel excavation,
 the final use and
 shape of the tunnel and appropriate risk.

8. 1. CONVENTIONAL METHOD
2. TUNNEL BORING MACHINE (TBM
METHOD)
3. NEW AUSTRIAN TUNNELING
METHOD (NATM)

9.  The term New Austrian Tunneling Method
Popularly Known as NATM got its name from
Salzburg (Austria).
 It was first used by Mr. Rabcewicz in 1962. It got
world wise recognition in1964.
 The first use of NATM in soft ground tunnel in
Frankfurt (Europe) metro in 1969
WHERE NATM IS USING IN INDIA
Presently it is using widely in Kashmir Railway projects.

10.  The New Austrian Tunneling Method is a support
method to stabilize the tunnel perimeter by means of
sprayed concrete ,anchors and other support and
uses monitoring too control stability.
 Main idea is to use the
geological stress of the
surrounding rock mass to
stabilize the tunnel itself.

11.  SURVEY & PROFILE MARKING
 DRILLING HOLE (1.5 TO 4m)
 LOADING EXPLOSIVE
 CHARGING (20 – 30 min)
 BLASTING
 DEFUMING THROUGH VENTILATION PIPE
 REMOVAL OF MUCK
 SCALING/CHIPPING WITH BOOMER
 SHOTCRETE Ist Layer ( upto 50mm )
 SURVEY
 SUPPORT SYSTEM (Wire Mesh , Steel Rib/Lattice girder )
 SHOTCRETE 2ND LAYER (150 – 200mm)
 Systematic Rock Bolting

12. DRILLING
 DEFINITION :- The process of making a hole in
hard materials such as rocks and earth.
COMPONENTS :-
Drill- Type of tool which holds the drill bit and
rotates it to provide axial force to create a hole.
Drill bits- Cutting tools used to create cylindrical holes
• Drilling is used to make hole in the rock mass ,
• A hole is upto 4 m long depending upon the class of
rock mass .

13.  TYPES OF EXPLOSIVES-
Explosives based on chemical nature
 High or detonating explosives-
Process is extremely rapid, almost instantaneous.
 Low or deflagrating Explosives-
Low velocity of burning and produce pressure by progressive
burning
 Explosives based on availability
 Powder explosives
 Disruptive explosives or Dynamites-

14.  A exporter having a red light/button used for blasting
 Start charging face at least 15 minutes after start drilling
out a safe position.
 Charging should be done always from the top to bottom , it
should be done 200m away from the explosive area.
 Take blasting cord with in the basket and correct detonator
straight after hole is finished charged.
 As soon as charging out of the basket is done prepare
ignition- cable and correct electrical dets.
 Push red light for blast after it give signal.
 Wheel-loader and Dumper trucks have to be organized
before blasting and placed inside Tunnel.

15.  Control Blasting
 Volume excavation difficult to achieve
 Permission & license is must for usage, storage &
transportation
 Limited permission available for usage, when its must
 Usage is still restricted like drill & blast
 DEFINITION- The process of breaking rocks into smaller pieces by use of
explosives.
A picture of phase with exploxive loading
Ready for blasting.

16. VENTILATION IN TUNNELS
Ventilation is required because of :
 Remove Dust and Gas caused by drilling, blasting,
loading of excavated materials and Shotcreting.
 Exhaust gas and smoke discharged by diesel
 Poison gas made from explosive or organic
solvent
 Poison gas, flammable gas or oxygen shortage
gas in ground
 High temperature and high humidity

17.  Mucking is a process in which muck is carried in the
dump truck after blasting and throw outside the tunnel.
 Mucking has to be not lower than the bottom plate of
last lattice girder.
SCALING/CHIPPING
Scaling/Chipping in progress
Scaling/chipping is done with boomer
machine to remove
The muck which stick to the
Phase.

18.  SHOTCRETE is the generic name for cement, sand and fine aggregate
concretes which are applied pneumatically and compacted dynamically
under high velocity”.
 Pre-shotcrete
First the profile and the after needs to be washed down so that there will be
a good connection between rock and shotcrete. Areas where are over break
situations should be sparyed first with a thin layer (max 10 cm). The
shotcrete needs to be sprayed from the bottom upwards to have a good
abutment for upper shotcrete.

19.  Wire mesh :- Wire mesh is used to support small
pieces of loose rock or as reinforcement for shotcrete.
 Stabilization of applied shotcrete until setting and
hardening
 Increase of shear strength
 Preventing dropping of
shotcrete portion after
cracking or failing of the
lining.
 SIZE: Standard size is
150 x 150 x 6 mm

20. LATTICE GIRDER :-
 It is used when rock is loose.
 It is used in class C2 , D and F of rock.
 Functions of Lattice Girder
 Steel Rib/Lattice Girder Composite structure of lattice girder
and concrete confined to load distribution.
 Carrying of “Green” shotcrete.
 Profile control
 Support for forepoling
Placing of lattice girder

21.  FUNCTIONS OF SECOND SHOTCRETE
1. As sealing Shotcrete:
Avoids first loosening of the surrounding ground.
Closes joints and prevents fall-downs; so activating
the rock arch.
Seals the surrounding ground.
2. As main shotcrete (carrying member):
To carry the load introduced by the ground in the
lining.
Second layer shotcrete is sprayed to cover the lattice
girder
Shotcrete is sprayed upto 150-200mm

22.  Mark the position of rockbolts with spraypoint. Start drilling from
the top down, so that the basket is able to work above the
boom, as soon as the first hole is drilled. Depend on what kind
of rockbolt needs to be installed carry on like explained below –
 Rock bolt are used to support the upper part of the tunnel.
 It is inserted at an inclined
angle 40-60 degree in the
rock.
 SDA :- Self Drilling Anchor
 SN :- Store Norphus
Rock bolt
TYPE OF ROCK BOLT

23.  Geology is very important while designing a tunnel.
 The method adopted for tunneling is based on the type of rock and
geological conditions.
 Tunnels are safer to the earthquake from the other on ground
structures.
 ventilation of tunnel is very important in tunnel during the
construction and after the construction.
 NATM approach of design and execution of the tunneling
in soft ground is advantageous and scientific way in comparision to
the old way of tunneling.
This system monitors rock mass deformation and design the
support system with reference to the rock mass type .