Smoothbore Shaft Linings | Tunnels & Shafts

FP McCann has developed a comprehensive range of smoothbore shaft linings. Each size is specifically designed to meet the tunnelling industry’s exacting and varied needs, recognizing the key criteria as being strength, stability and the capability of performing in all types of ground conditions.

Design Features

All rings, with the exception of the cutter choker, comprise of ordinary segments and two top segments. The top segments have one tapered cross joint so that they can be installed with an EPDM gasket. The cutter choker comprises all ordinary segments.

Sealing

FP McCann is the only precast concrete manufacturer to supply pre-fitted, tailor-made EPDM rubber gaskets on the full range of smoothbore shaft and tunnel linings. The gaskets provide an immediate water-tight seal on construction and are fully compliant with the requirements of the British Tunnelling Society specification. Speed of build, safety and increase on-site productivity are key benefits.

Connection

Cross joint connections are made using a spear bolt passing through a pocket in one segment and a plastic socket in the adjacent segment. Circle joint connections are made using a T bolt passing through a hole in one segment and into a T box in the adjacent segment. Bolts are designed to fully compress the gasket. All connections are sherardised. (Other finishes to fittings, including galvanized, are available on request). FP McCann manufactures front bolted and back bolted linings on all diameters. For diameter 10.5m and above, universal linings are available to allow for changes in construction method. (Build manual available upon request).

Ring Types

Segmental ring types provided by FP McCann:

Segmental rings in stock are front or back colted.

Standard rings
Corbel rings
Recessed rings (Standard, choker or cutter choker)
Choker rings
Combined Cutter Choker rings

Mix and Reinforcement

Each segment is wet cast to achieve a smooth internal finish. The concrete mix provides a Design Chemical Class 4 (DC4) with a minimum 28 day characteristic cube strength of 55 N/mm². Alternative mixes are available. The segments are reinforced with either a reinforcing cage or structural synthetic and steel fibres to suit both design and customer requirements.