Product category:
Ground Engineering
News Release from: Tensar International | Subject: Tensar SS30 bi-axial geogrids
Edited by the Buildingtalk Editorial
Team on 29 July 2003
Safety and Stability For Piling Rig
Platforms
Safety and stability are of paramount importance for Royal Docks piling rig platforms with Tensar Geogrids.
For the latest phase of building at the Royal Docks, in the heart of London's Docklands, consulting engineers KMG Partnership were concerned about the problematic ground conditions while piling for proposed six storey office blocks Tensar SS30 bi-axial geogrids were specified as an economical and rapid technique for establishing a stable working platform for the heavy piling rigs, and to ensure both the safety and the efficiency of the operations
This article was originally published on Buildingtalk on 15 Jul 2003 at 8.00am (UK)
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Inadequate working platforms and access have long been recognised as significant sources of accidents with piling rigs, especially without proper site investigation information or using true rig loadings in calculations.
The Federation of Piling Specialists (FPS) in the UK have led a major Health and Safety Initiative to ensure the proper design, installation and maintenance of platforms and access.
In this project at the Royal Docks, KMG consulted Tensar International at an early stage for its design input into establishing safe platform performance.
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The heavy piling rigs were required to operate over a layer of between 1 and 6 metres of poor quality made ground from the original dock excavations, overlaying a further 2 to 6 metres of alluvium containing peat horizons and, beneath that, sands and gravels.
The undrained shear strength (Cu) for the fill and alluvium was taken as a representative 25 kPa.
This had to withstand a critical loading pressure of 250 kPa from a Cementation R928 CFA/Rotary bored piling rig, imposed over an area of approximately 3m.
Tensar SS geogrids have been shown to mobilise a load-spread angle of at least 45 degrees when placed within good quality, compacted granular fill.
On this ground, the conditions dictated a safe platform depth of 675 mm, comprising two layers of Tensar SS30 bi-axial geogrid and 75mm down fill.
With a square grid aperture size of 37mm X 37mm (approx.), the specified fill interlocks with the geogrid to maximise the angle of load spread within the platform, and resists shear load to optimise the load bearing capacity.
The geogrids are supplied in 50m X 4m rolls and laid with a simple overlap of typically 400mm.
Larger grid apertures are available from Tensar for coarser fills.
The Tensar manufacturing process produces a unique grid structure, consisting of full strength junctions and stiff ribs, which present a thick square leading edge to the aggregate.
This allows the aggregate particles to grip the geogrid and forces an effective mechanical interlock, which prevents lateral movement and dilation of the particles, so that a very high effective angle of shearing resistance is mobilised.
Contract details: Consulting engineers: KMG Partnership Main Contractor: Bowmer and Kirkland Ltd Working Platform Installer: AD Bly Construction Ltd.
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