We typically use two specific techniques to undertake trenchless construction – slurry pressure balanced microtunnelling and pilot auger soil displacement. Either is used to address access challenges, site footprints, ground conditions, minimise urban disruption or, to efficiently cover large distances. Both techniques are used to construct critical water, wastewater, drainage, or energy utilities infrastructure.
Slurry Pressure Balance
The slurry pressure balanced technique can be used in all ground conditions and greatly limits the potential for over-excavation during tunnelling operations. Slurry pressure balances machines are commonly used to construct pipelines between DN300 and DN2100 over short or long distances. 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. 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.
Pilot Auger Soil Displacement
The pilot technique is used in soft, dry or wet non supporting soils for small diameters, typically DN150, DN225 and DN300 and to construct pipelines up to 90m in length. The technique requires a small diameter pilot rod to be pushed through on line and grade from the launch to reception shaft. Once through, a casing pipe with auger attached is used to remove material along the alignment with the carrier pipe being progressively installed behind the casing to construct the pipeline.