Case Study: Temporary Sheet Pile Design for Crossness STW, London

Temporary Sheet Pile Design for Crossness STW, London

Contract No:C848
Client:TAMESIS JV - (Laing O'Rourke / Imtech Process)
Location:Crossness STW, London
Value:Approximately £600,000.00
Summary:Sheet Pile Design, supply, installation and extraction of steel sheet piles to form various temporary earth retaining sheet pile cofferdams and sheet pile trenches.

Sheet Piling UK Ltd were employed by Tamesis JV for the sheet pile design, pile supply, sheet pile installation and extraction of steel sheet piles to form various temporary earth retaining sheet pile cofferdams and sheet pile trenches to facilitate the installation of new pipework and the excavation and construction of associated RC structures etc.

Close liaison between Sheet Piling UK Limited and Tamesis has been necessary to ensure that the sheet piling and sequencing of propping installation / removal was compliant with the proposed pipe laying and back-filling activities.

In excess of 2200 no. sheet piles have been installed in lengths varying from 11.50m to 15.0m. Only a proportion of the total sheet pile requirement was supplied to site, and re-use of sheet piles on different structures was an important consideration to minimise costs. Therefore, the best and most economical use of the sheet piles was dependent upon careful planning and design by SP.UK Ltd in conjunction with Tamesis JV.

The steel sheet piles were propped as required using proprietary hydraulic type modular frames, designed and installed by others to withstand frame loadings supplied by Sheet Piling UK Limited.

In order to remove propping to facilitate pipe installation in some cases, a sacrificial concrete slab was required to provide sufficient low level support in lieu of the previously placed steel propping.

The general soil profile for this site consisted of Made ground over soft to very soft Alluvium over medium dense Sandy Gravels at varying depths. The pile design required that a minimum embedment into the underlying sandy Gravel soils was required for stability.

The sheet piles were generally installed using a tracked Telescopic Leader Rig mounted with a high frequency vibro hammer in association with a mobile service crane.