Final Lining

The final lining is a critical component in underground construction, playing a pivotal role in ensuring the durability and structural strength of the finished structure. It also serves as a base for essential service installations like ventilation, aeration, and lighting. An innovative aspect of this phase is the use of steel fibres for fibre-reinforced concrete, which can effectively prevent micro-cracks and sometimes replace traditional reinforcing bars, enhancing the overall integrity and longevity of the construction.

Beneath the visible final lining lies a layering system that ensures the tunnel’s functionality and safety. This system includes waterproofing, which is essential for maintaining the tunnel’s structural stability and safety: polymeric geomembranes provide extremely low permeability to prevent water ingress and infiltration. Additionally, an underlying layer of protection is essential: MacDrain is a 2-in-1 geocomposite which protects the waterproofing layer and also functions as a drainage system to remove water from around the excavation profile.