NATM ppt sumit

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

1. New Austrian Tunneling Method BY :- Sumit mandla A presentation about Under The Guidance of: ER. ASSISTANT PROFESSOR Department of Civil Engineering in KITE, Jaipur ( 13EKTCE453 ) NATM

2. What is Tunnel ? 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 W hen the lane encounters an obstacle such as a mountain to avoid bypassing the obstacle B uilt sometimes to overcome a water obstacle as a replacement for building a bridge above it . B uilt 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. ADVANTAGES OF TUNNEL 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. Shapes of Tunnel 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. Commonly Used methods IN TUNNEL CONSTRUCTION CONVENTIONAL METHOD TUNNEL BORING MACHINE (TBM METHOD) NEW AUSTRIAN TUNNELING METHOD (NATM)

9. INTRODUCTION OF NATM 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 K ashmir Railway projects.

10. New Austrian Tunneling Method (NATM) 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. Work sequence & Element in NATM METHOD 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 2 ND LAYER (150 – 200mm ) Systematic Rock Bolting

12. DRILL AND BLAST METHOD 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. LOADING EXPLOSIVE 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. CHARGING 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. BLASTING 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 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 SHOTCRETE is the generic name for cement, sand and fine aggregate concretes which are applied pneumatically and compacted dynamically under high velocity ”. P re- 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. SUPPORT SYSTEM 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. Second Shotcrete FUNCTIONS OF SECOND SHOTCRETE 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. Rock Bolt 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. CONCLUSION 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 .

24. THANK YOU