The Use of Tunnel Boring Machines for Driving Small Area Tunnels in Sandstone and Shale

The Metropolitan Water Sewerage and Drainage Board drives approximately 9 km of sewage tunnels annually, predominately through rock. These tunnels have a small cross sectional area and have been driven by conventional techniques (i.e. drilling and blasting) in the past. In 1974 the Board took delivery, on a hire basis, of the Atlas Copco's Mini Fullfacer (Mini 1), tunnel boring machine. Since then, the Board has driven eight sewage tunnels, varying in length from 0.3 km to 3.1 km, by tunnel boring machines. The paper gives a description of the history, layout and operation of the Atlas Copco tunnel boring machine used by the Board. The economics and the suitability of using tunnel boring machines for driving small area tunnels is highlighted with special reference to the eight tunnels already driven by the Board using tunnel boring machines.