Pipe Jacking - Micro Tunneling
Microtunnelling is considered as a remotely controlled mechanical tunneling systems pipe jacking. Shield boring and pipe jacking are conducted entirely by remote control, managed by an operator from a control console in the cabin above ground where no worker entry is required inside the shaft or tunnel. The spoil is removed from a cutting head placed in the new pipeline which is advanced by pipe jacking. In microtunnelling, the excavation is always trenchless and pipe jacking, excavation, and transport of spoil are all take place simultaneously. The only excavation works required is for the construction of drive and reception shafts. Microtunnelling do not require long and extended stretches of open trench for pipe laying and is hence deemed to provide a much safer working environment.
Special boring machines or shields used in microtunnelling are called microtunnelling tunnel baring machines (MTBM), they are electrically powered and attached to the head of the pipe that follows the path of the tunnel as it is being bored. Microtunnelling machines have been developed to work from drive shafts in almost all types of ground conditions It is essential to identify these conditions as they will determine the types of machine to be used, as well as the type of cutter head, the spoil removal system, and the jacking forces likely to be required. The selection of cutter head has to be done carefully to deal with the predicted ground conditions, with the appropriate cutting tools and crushing devices for the range of gravels, sands, silts, and clays.
Microtunnelling machines are featured with laser guidance control system and computerized monitors that steer the machine with a high degree of accuracy. It is noted that pipelines laid in this way are more accurate and evenly stressed than those lay using the open trench method.
