Technical Tunnelling Components


The Dowelock system is a boltless connection device for joining two segmental rings together on the circumferential joint. Dowelock is designed to operate with compressible gaskets (Hydrophilic or Elastomeric with or without molded corners). The performance of the dowel is compatible with the compression characteristics of these types of gasket and copes with varying joint gaps whilst minimising gasket offset.

Dowelock consists of a connecting dowel moulded from a high strength, high durability plastic, together with two locking assemblies; one cast into each of the adjacent tunnel lining segments. These locking assemblies incorporate patented locking collets that allow the dowel to enter with a minimal insertion force and then lock, thus preventing the dowel from withdrawing. These collets are retained in such a way as to allow the dowel to be entered off line as they have the capability to rotate whilst the dowel is inserted and therefore aligning and securing the precast concrete units.

Product range includes Dowelock 20, 30, 38 and 45 with tensile strength ranging from 60kn to 20 tons+



Grout Sockets

Designs and manufactures a wide range of grout/lifting socket assemblies, bolting systems, alignment dowels and miscellaneous products to work alongside the Dowelock system





Spear Bolt

Fast Thread Sockets And Bolts : TTC’s spear bolt sockets are available in different lengths and diameters depending on segment size, weight and type of sealing system proposed, they are designed so that cross threading is impossible due to it’s ‘reeled’ thread design which is also self cleaning and faster to install. Dowels that align the segments are available in a range of sizes to make construction easier, quicker and safer.


Alignment Dowels

TTC manufactures a range of alignment dowels for use on the circumferential joints. These dowels can also be used to increase the shear resistance and can be manufactured from plastic or metals in different grades. Additionally offers its Dowelock Dowel Pins in metals of different grades if a particularly high resistance to shear is required. This allows clients to utilise the standard Dowelock housings and collets and negates the need for different ring fittings or additional segment moulds..