Sheet Piling Installation, Beckton STW, London
|Client:||TAMESIS JV - (Laing O'Rourke / Imtech Process)|
|Value:||Approximately £1.1M (following credits on sheet piles)|
|Summary:||Design, supply, installation and extraction of steel sheet piles to form various temporary earth retaining cofferdams and trenches.|
Sheet Piling UK Ltd were employed by Tamesis JV for the design, supply, installation and extraction of steel sheet piles to form various temporary earth retaining cofferdams and trenches to facilitate the installation of new pipework and the excavation and construction of associated RC structures etc.
Close liaison between Sheet Piling UK Ltd 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 3900 no. 12.0m long sheet piles have been installed. 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 Sheet Piling UK Ltd in conjunction with Tamesis JV.
The 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 Ltd.
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, over firm to stiff Clay at varying depths. The sheet pile design required that a minimum embedment into the underlying sandy Gravel soils and Clays was required for stability and water cut-off.
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. Sheet piles adjacent to existing sensitive structures and/or pipelines were installed using a Silent Piling Vibration Free Giken Piling UP.150 Hydraulic Piles Press in conjunction with water jetting. Due to the nature of the underlying sandy gravel soils, prior to the Giken Piling installation, pre-augering was deemed necessary to reduce the insitu density and remove any large cobbles etc. This was carried out with a tracked telescopic leader rig mounted with an auger drive and flight augers.