Sprayed Concrete Lining (SCL)

Sprayed concrete can be used in a variety of applications, including tunnelling projects - primary & secondary linings and for regulating layers to mitigate significant deviations from line and level.

Sprayed concrete is also used in the New Austrian Tunnelling Method (NATM) to provide temporary support in soft or unstable geological conditions.

Traditional methods of sprayed concrete lining (SCL) tunnels comprise a temporary primary lining of sprayed concrete with a sheet membrane inside and a permanent cast in-situ concrete lining, usually reinforced with steel bars or steel fibres within the shotcrete matrix. Although it is widely accepted that sprayed concrete can be used as a permanent material, the traditional methods still are applied to the majority of tunnels. This can prove to be wasteful in terms of economics, time and materials.

Engineers and designers are now providing design solutions for the use of permanent sprayed concrete with a variety of waterproofing solutions through their involvement on major projects in the UK – in particular in soft ground tunnelling conditions.

 

Design solutions have ranged from:
  • Permanent sprayed concrete lining
  • Sprayed onto a sheet membrane in a drained tunnels
  • Permanent waterproof sprayed concrete lining in impermeable ground
  • Permanent sprayed concrete lining applied in two passes with spray-applied waterproofing membrane
Sprayed concrete lining applied to brick railway arch – Carlisle - Cumbria
In addition to tunnelling works (new construction), sprayed concrete linings can be applied in other environments such as:
  • Culvert rehabilitation and new construction
  • Flood defence schemes
  • Mining and excavated ground support
  • Shaft lining and shaft reinforcement
  • Brick railway arch strengthening
  • Tunnel portals
  • Water treatment plants and water retaining structures
Before: Sprayed concrete lining (SCL) to existing culvert - River Wantsum, Kent
After: Sprayed concrete lining (SCL) to existing culvert - River Wantsum, Kent
This sprayed concrete application (usually shotcrete) requires a high degree of mechanisation and well trained nozzle operators to be effective. All GSSL personnel are trained to national standards (SCA – Sprayed Concrete Association and NVQ 2 minimum) together with training in concrete pump and robotic spraying for this specialist type of shotcrete works.

Successful sprayed concrete repair requires the combination of many aspects of modern concrete technology particularly concrete admixture chemistry, combined with modern materials handling technology.

Sprayed concrete lining (SCL) to existing flood-damaged culvert - Todmorden, West Yorkshire
Sprayed concrete lining (SCL) to existing flood-damaged culvert - Todmorden, West Yorkshire

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The increasing demands for cost-effectiveness and the protection of health and the environment mean that sprayed concrete has been in continuous development for the last few decades with a proven track record.
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