As part of a Wessex Water capital scheme to boost waste water services to the increasing population in and around the Somerset town of Yeovil, FP McCann’s back-bolted caisson shaft segment rings have been used to build a 7.50m id pumping station chamber.
The contract to build the shaft and other associated civil engineering works was awarded to Terra Solutions, one of the UK and Ireland’s leading trenchless contractors, specialising in tunnelling and pipe repair.
The shaft was sunk under its own weight using the caisson method and the shaft wall was formed using 8 no. FP McCann 7.50m ID back-bolted standard precast concrete rings. The steel cutting shoe was installed by Terra. Prior to the pouring of a concrete guide collar around the outside of the segments, the base segmental ring was constructed and a second ring was placed on top. Once the collar gained the required strength, the third ring and subsequent rings were placed on top, thereby allowing the shaft to sink under its own weight.
Once the shaft build was completed, concrete was poured into the base to form a 1.5m deep plug, and a further 500mm reinforced concrete base was pumped in, dowelled and tied to the shaft wall to complete the solid chamber.
To complete the watertight pumping chamber build, FP McCann supplied the reinforced concrete cover slab. This was delivered in three sections, the heaviest of which weighing just over 20 tonnes.
Commenting on the shaft build, Warren Patton of Terra Solutions said, “The concrete segments supplied by FP McCann were connected on site and each ring descended under its own weight as the ground was excavated beneath. Once commissioned this 8 metre deep chamber will significantly add to the capacity to manage the waste water in Yeovil”.
Key features and benefits of FP McCann’s back and front bolted smoothbore shafts are: