Tunnel lining formwork

Tunnel formwork is produced in various cross-sectional shapes such as horseshoe, circular, elliptical, etc., depending on its intended use (for roads, waterworks, military applications, etc.).. Common Length Dimensions in Technical Terms tunnel lining formwork Tunnel formwork with dimensions of 6 and 9 meters is applicable in road tunnels, railway tunnels, aqueducts, dam tunnels, and wastewater tunnels.

Tunnel formwork is generally composed of two main parts: the shell and the ribs. Usually, segments with a width of 1.5 meters form the shell.

Tunnel lining formwork can be classified into two types based on their dimensions in terms of the opening and closing mechanism:

  • Hydraulic tunnel formwork
  • Mechanical tunnel formwork.

In the hydraulic type, due to the weight of the tunnel formwork, the opening and closing of segments and petals are carried out using hydraulic jacks. In the mechanical tunnel formwork, this is done using manual or oil jacks, as the formwork is lighter.

The operational mechanism with tunnel formwork functions in the following manner: after each concrete pouring stage, initially, the petals are retracted using the side jacks, and then the entire shell assembly settles down through the use of the base jacks. The rib is moved along the rail to a new position, and after lubricating the surface sheet for ease of separating the tunnel formwork from the concrete, it is adjusted to the desired height