- What is microtunnelling?
- Microtunnelling is the term referred to for installing pipes by remote control where person entry is not practical. In brief, excavation at the face is carried out by the machine tunnelling head, and spoil is removed by slurry pumping, conveyor or auger.
- What is pipejacking?
- Pipejacking is a method using hydraulic rams to push pipe sections directly behind a cutting head, shield or tunnel boring machine (TBM) to form a continuous string of pipes in the ground. Strictly, the term applies to any pipe diameter and shape but this term is often taken to mean tunnels where person entry is permissible, 1000mm is a common minimum internal size.
- Where and when can microtunnelling and pipejacking be used?
- Microtunnelling and pipejacking methods are usually specified when conventional open trench methods are impractical for pipelines to be installed due to depth and / or under roading networks, railway lines, buildings etc.
- What types of pipe material can be installed using microtunnelling or pipejacking methods?
- Typically, reinforced concrete pipe is used, however ceramic, polycrete, glass reinforced plastic (GRP), HDPE, steel and even plastic can be installed.
- What drive lengths can be achieved?
- Longer drive lengths are being achieved all the time as a result of improved equipment and techniques.
In general, the smaller the diameter – the shorter the length. For example, a machine designed to install 450mm diameter pipe may be limited to around 110 metres whereas a machine designed to install 2500mm diameter pipe can range over 1,000 metres. - Are there ground conditions that microtunnelling and pipejacking methods are not suitable for?
- Pipelines have been installed in ground conditions ranging from saturated running sands, soft clays through to dense rock.
Tunnelling machines are selected to suit the ground conditions to be encountered. Accurate geotechnical information is required for selection of the most suitable machine for installing any pipeline. - At what depth does it become economical to use trenchless methods?
- This depends on where the pipeline / conduit is being installed. Within the road carriageway where reinstatement or disruption to the general public is an issue, trenchless methods may be the more favourable option at any depth. However, in a Greenfield situation the cost and time benefits may balance out at around the 4 metre deep mark.
- What grades can be installed using microtunnelling and pipejacking methods?
- Using laser and gyroscopic guidance to control the machine head, any grade specified can be installed.
