FP McCann’s smoothbore shaft segments form pumping house

The upgrading of the treatment plant will facilitate the construction of a major development proposed for the area. The contract, part of Severn Trent WaterÂ’s AMP6 programme of works, has seen a 6 metre internal diameter inlet pumping station constructed.

Specialist shaft and tunnelling contractor, Delta Civil Engineering, has completed the sub-contract works on behalf of STWÂ’s AMP 6 construction project delivery consortium CIM6 (Costain integrated with MWH UK)

The shaft was constructed using the wet caisson method with FP McCannÂ’s 6m ID back bolted precast concrete rings forming the shaft wall. The shaft was sunk to a depth of 8m using DeltaÂ’s unique jacking system which guarantees a vertical structure upon completion. The design of the structure included the use of a panelled choker ring, manufactured by FP McCann, which sat on top of a FP McCann concrete cutting edge, a combined choker/cutter incorporating recesses cast into the intrados, in order to provide shear interaction with the in-situ concrete base and to resist floatation.

Speaking on behalf of Delta, General Manager Neil Bracken says, “This shaft build option is extremely efficient, allowing the team to quickly complete connections on the external face which itself provides significant safety benefits”.

Birmingham based RNP Associates were commissioned by Delta to undertake the geotechnical design including the floatation calculations for the shaft during installation and for the permanent condition once installed. RNPÂ’s design also included the sizing of the jacking collar to resist jacking uplift forces during construction.

A mass reinforced concrete slab benching completed the structure ready to hand over to the client for subsequent M&E installation.

Delta Civil Engineering were one of the first contractors to utilise FP McCannÂ’s new backbolted segment system on a similar pump house in Bicester and the response from their miners has been very encouraging.

FP McCann’s smoothbore shaft segments are all factory fitted with EPDM rubber gaskets which provide an immediate water-tight seal upon construction. Cross segment connections are made by passing a spear bolt through a pocket in one segment and screwing it into a threaded plastic socket in the adjacent segment. Circle joint connections are made using a ‘T’ bolt passing through a hole in one segment into a ‘T’ box in the adjacent segment. Bolts are designed to fully compress the gasket.

Key features and benefits of FP McCannÂ’s back and front bolted smoothbore shafts are:
Smooth internal faces
Simple locking process
Speedy installation
Increased site productivity
Safe build features
Technical advice and support​