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Auger Boring |
Since the auger is not capable of providing continuous face support, groundwater is problematic as it can cause the soils to flow and flood the steel casing. As a result, auger boring is typically limited to stable soils located above the water table or in those soils that can be dewatered along the entire alignment.
Auger boring, traditionally known as the “bore and jack” method, involves simultaneously jacking a steel casing forward in segments while removing the spoils via a rotating auger flight. A cutting head is attached to the leading edge of the auger, which protrudes just ahead of the steel casing. The steel casing is pushed forward using hydraulic jacks located within the jacking pit. Rotation of the auger flights removes soil at the face while carrying the spoils back to the jacking pit where they can be removed using a clam shell or excavator.
Once the casing reaches the receiving pit, the cutting head will typically be removed for reuse. Product pipe is installed within the casing, and the resulting annular space may either be grouted or left open for future capacity upgrades.