Tunnel Formwork

Tunnel Formwork

The complexities of below ground construction, particularly in relation to the limitations on access, mechanical handling capabilities and space are often challenging. Cordek have a depth of experience accrued through previously undertaken tunnel related projects, providing bespoke formwork solutions for applications including: Intersections and cross passageways, Soft Eyes for Shaft Wall Construction, Transitions for Escalators, Ventilation Shafts, Pedestrian Walkways and Service Tunnels.

Each former is designed to meet the specific requirements of the project including the size, shape, finish and number of re-uses. Using this information, our designers will select the most appropriate material for each former and create a 3D CAD model for approval, which would then be used for CNC machining of the finished formwork solution.

Features

  • Manufactured to meet project specific requirements
  • Available in a wide range of materials
  • CNC machined for consistent, tolerance-controlled surfaces
  • Re-usable where applications of the same size, shape and profile are repeated
  • Can be supplied in a unitised format for manual handling or limited access purposes
  • Basic, Ordinary, Plain & Special Finishes achievable*

*Please refer to National Structural Concrete Specification (NSCS) Edition 4 guidance available below.

Applications

Used for the construction of cast in-situ reinforced concrete tunnel structures with either complex or non-standard geometries, profiles and sizes.

Design

Tunnel Formwork

When developing a tunnel former design, the following factors should be considered in addition to reviewing any CAD drawings, 3D models, specifications etc that are available:

  • Dimensions, geometry and features
  • Required concrete finish
  • Proposed number of uses – single or multiple
  • Loadings – specifically relating to the proposed concrete pour depths
  • External structural support method
  • Delivery method, unloading requirements and access restrictions
  • Positioning, installation and sequence of construction
  • Striking, removal and re-use or disposal

Once the project requirements have been confirmed, a conceptual design can be completed along with provision of a quotation confirming proposed material type, features, quantities, manufacturing lead time and costs.

Materials & Finishes

Tunnel Formwork

Typically, Cordek tunnel formers are manufactured from one of the following material types:

  • Filcor Expanded Polystyrene (EPS)
  • Filcor EPS with ABS skin
  • Filcor EPS with Sheet Fibreglass skin
  • Filcor EPS with a spray applied Polyurea skin
  • Glass Reinforced Plastic (GRP)

One of the factors determining the most appropriate material used to manufacture a tunnel former is the required concrete finish. Further information in relation to the classification of concrete finishes can be found within the National Structural Concrete Specification (NSCS) Edition 4 guidance, a copy of which can be downloaded from the Certification, Guidance and Approval section below.

Manufacture

Tunnel Formwork

Once approved, the agreed 3D CAD Model will be converted to CAM data, allowing accurate manufacture of the tunnel former via CNC hot wire cutting and / or 5-axis routing dependant on factors such as material type, complexity of shape / profile and required tolerances.

In some instances, due to the required dimensions of the formwork solution, it may comprise of a number of individual units that require assembly on site. This can prove advantageous in certain applications, such as those that have no mechanical handling resource or reduced restricted access.

In cases such as these, features such as tie bolt locations can be incorporated within the design to secure adjoining units together, aiding alignment during the installation process.

Downloads

Data Sheets

Product Issue Date Version Size Download
Filcor Data Sheet 03/2021 8 405.9 KB

Standard Details

Product Issue Date Version Size Download

MSDS Data Sheets

Product Issue Date Version Size Download
Expanded Polystyrene MSDS 06/2017 5 137.3 KB

Certification, Approval & Guidance

Product Issue Date Version Size Download
National Structural Concrete Specification (NSCS) Edition 4 1.2 MB

Brochures

Product Issue Date Version Size Download
Construction Solutions 01/2020 2 6.6 MB

NBS Clauses

Our NBS Clauses are hosted on the external website - view NBS Clauses

BIM Library

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Case Study

Farringdon Station Escalator Shaft 2

Cordek were tasked with providing a formwork solution to enable the main contractor to cast the ‘knuckle’ intersections between the escalator shaft and the levels above and below.