Tunnel access and ventilation shaft: What is at stake?

Access shafts (ranging from 10 to 120 meters deep) connect the underground to the surface, providing highly-critical access points for Tunnel Boring Machines (TBMs).

Ventilation or Evacuation tunnels are built along the main tunnel(s) to increase accessibility and potential evacuation needs.

Since the construction of tunnels is often carried out in close proximity to existing structures and densely populated areas, retaining structures, usually consisting of diaphragm walls, require specialist engineering in order to optimise safety, scheduling and cost.

Complex geological profiles and ever greater excavation depths raise additional challenges that make this expertise even more crucial.

How VSL can help you

VSL-Intrafor specializes in constructing deep access or ventilation shafts of 80+ metres or more. Their expertise in diaphragm walls, and long-term involvement in dense environments and complex geology is showcased particularly in Hong Kong.

Commanding over 400 pieces of specialized equipment, including state-of-the-art diaphragm wall cutters (capable of exceeding depths of 120m), trench cutters, and low-headroom equipment, VSL-Intrafor also employs a highly-experienced team of mechanical and hydraulic engineers.

Together, these resources allow VSL-Intrafor to deliver in both capacity and flexibility to meet tight deadlines.

What are the VSL tunnel access and ventilation shaft solutions?

A design and build package, including:

  • Design and engineering
  • Installation of access and ventilation shafts,
  • Installation of retaining wall structures such as diaphragm walls and VSoL wall systems,
  • Specialized equipment


Solutions that can be combined with access or ventilation shafts

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