The slurry pressure balanced technique can be used in all ground conditions and greatly limits the potential for over-excavation.
Dedicated machines are commonly used to construct pipelines between 300mm and 2,200mm OD over long distances under live rail, roads and water ways.
The slurry generated and recycled by the tunnelling process is used to counterbalance earth and hydrostatic pressure at the face of the machine to provide immediate tunnel support. The technique is especially beneficial in ground consisting of a high water table.
As the machine progressively moves forward constructing the tunnel, rigid jacking pipe is immediately thrust behind the machine to ensure the tunnel is lined with structural pipe, ensuring the integrity and full continuous support of the tunnel at all times.