Tunnelling Techniques

Introduction

• Need to consider:

– Type of ground

– Method of tunnelling

– Removal of spoil

– Ground water control

Types & Methods

• Used for road, rail, water, gas, sewerage, storm water and services

• Techniques are numerous depending on ground & permanent use:

– Hand

– Trenchless technology

– Traditional

– New Austrian (NATM)

– Boring

– Immersed tubes

Traditional

• Usually rock, up to approx 200m² csa

– Drill & blast

– Spoil loaded into trucks

– Can use benching

– Propping may be required

NATM

• New Austrian Tunnelling Method

– Designed by the Swiss used under licence in UK by Caledonian Mining Company Ltd

– Uses lattice girders, metal mesh and shotcrete

• Ease of use

Boring

• Rock needs to be classified

– Whole face boring

– Roadheaders

Immersed Tubes

• Lowering prefabricated tubes onto a pre-prepared sea or river bed.