NATM NEW AUSTRIAN TUNNELING METHOD

HISTORY 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. The basic aim of NATM is for getting stable and economic tunnel support systems.

DEFINITION OF NATM The New Austrian Tunnelling 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.

BROAD PRINCIPLES OF NATM Mobilization of the strength of rock mass Shotcrete protection Measurements Primary Lining Rock mass classification Dynamic Design

WHY NATM Flexibility to adopt different excavation geometries and very large cross sections. Flexibility to install additional support measures, rock bolts, dowels, steel ribs if required. Easy to install a waterproof membrane. Easy to install primary support, i.e. shotcrete. TBM (Tunnel Boring Machine) is not an effective method as compared to NATM .

SUMMARY OF THE PROCEDURE IN NATM SHOTCRETING AT THE EXCAVATED AREA(PRIMARY LINING) PLACING OF THE WIREMESH ALONG THE FACEOF THE TUNNEL ERECTION OF THE LATTICE GIRDER ALONG THE FACE OF THE TUNNEL PERTICULAR TYPE OF ROCKBOLTING SHOTCRETING THE WHOLE ARRENGEMENT(SECONDARY LINING)

SEQUENCE OF EXECUTION OF NATM

CONCEPT OF 3D MONITORING 3D MONITORING IS NEW TECHNIQUE USING FOR TAKING THE RIGHT ALIGNMENT OF THE TUNNEL OPTICAL TARGETS ARE USED FOR DETRMINIG THE COORDINATES FOR MEASUREMENTS THE COORDINATES SHOULD BE CHECKED DAILY IT IS NECESSARY FOR THE TUNNEL AS BY IT WE KNOW ANY DISPLACEMENT AND WRONG ALIGNMENTS

General Optical Target

General Optical Displacement Monitoring Free Stationing

POINTS TO CARRY OUT A SUCCESSFUL NATM PROCESS Consideration of rock mechanics Selection of a proper profile Design of flexible support and slender lining (in rock) Careful excavation Maintenance of rock strength, avoidance of loosening and over-breaks Direct contact of rock/soil and support Continuous control by geotechnical measurements Installation of support without delay and in correct sequence

WHERE NATM IS USING IN INDIA PRESENTLY IT IS USING WIDLELY IN KASHMIR RAILWAY PROJECT THEY ARE USING IT IN THEIR TUNNELS LIKE IN PIR PANJAL TUNNEL , T-74R, T-48 ETC

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