The open shield excavation (open shield) is a tunneling method in which the cutting wheel works in air, without internal pressure in the chamber. This gives it several particularities and advantages:
Main characteristics
Unpressurized chamberThe digging face remains visible, which facilitates inspections and replacement of cutting discs.
Dry evacuationThe debris is removed by conveyor belts or wagons, reducing sludge management and bentonite consumption.
Rigid structureThe shield acts as a temporary support ring, making it possible to advance in stable rock masses without the use of compensation fluids.
Compatibility with keystonesSegmented lining can be installed immediately behind the TBM if waterproofing is required.
Key benefits
Lower operating cost on competent soils by avoiding slurry pumps and separation plants.
Simplified maintenanceThe cutting discs are accessible, thus shortening downtimes.
Reduced environmental impactThe sludge footprint and associated logistics are minimized by not generating bentonite suspensions.
Superior feed rate when the geology is homogeneous, optimizing the construction time.
Security and controldirect visibility of the front facilitates early detection of loose blocks or lithological changes.
In summary, the open shield is the ideal choice for tunnels in hard rock or self-supporting terrains where a clean, fast process with lower operating costs compared to pressurized methods is required.
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