Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 2416 An introduction to pipe jacking and microtunnelling 4 DESIGN AND CONSTRUCTION METHODS PIPE JACKING EXCAVATION METHODS A range of pipe jacking excavation methods are illustrated. In most cases, the choice of method will also depend on the selection of the appropriate ground support technique: Tunnel boring machine (TBM) A shield having a rotating cutting head. Various cutting heads are available to suit a broad range of ground conditions. Cutter boom shield An open face shield in which a cutter boom is mounted for excavation purposes. Backacter shield An open face shield in which a mechanical backacter is mounted for excavation purposes. Pressurised slurry machine ‘Full-face’ tunnel boring machine in which the excavated material is transported from the face suspended in a slurry. Various cutting heads are available to suit a broad range of ground conditions and may incorporate internal crushers to deal with cobbles and small boulders. The pressure of the slurry is used to balance the groundwater and face pressure. Earth pressure balance machine (EPBM) A ‘full-face’ tunnel boring machine in which the excavated material is transported from the face by a balanced screw auger or screw conveyor. The face is supported by excavated material held under pressure behind the cutter head in front of the forward bulkhead. Pressure is controlled by the rate of passage of excavated material through the balanced screw auger or valves on the screw conveyor.