Fugro jack-up barge for Tideway site testing 05 Apr 2018

A new jack up barge from Fugro, carrying a full suite of geotechnical drilling, sampling and testing equipment capable of being mechanically folded, has saved time, cost and congestion during recent riverbed assessment for London’s major sewer upgrade, the Thames Tideway Tunnel.

Fugro Skate 2D negotiates 7.6m Blackfriars bridge

Two site investigation campaigns were carried out over a seven month period on the central section of the Tideway project for contractors Ferrovial Agroman and Laing O'Rourke. They involved drilling, downhole geophysics and testing to depths of 80m to provide ground risk and engineering data along a 10km stretch of the river.

More than 40 borehole and Cone Penetration Test (CPT) locations in tidal waters were sampled to suit the phasing of planning and design. The programme involved 55 bridge manoeuvres negotiating 12 of the Thames’ most famous, but also structurally diverse bridges, between Blackfriars and Wandsworth.

The Skate 2D jack-up barge was adapted by Fugro to allow leg handling and leg storage to be carried out by a single, self-equipped vessel that carried a centrally located, high capacity crane to self-lift the jack-up legs between a storage cradle on the stern of the vessel and positions at the platform jacking corners to allow execution of height restricted bridge manoeuvres. This eliminated the need for a support barge and crane to install, remove and transport the legs.

Site investigations to 80m achieved in tidal conditions

“Our uniquely designed, self-contained platform simplified logistical and health and safety management risks for the complex transits and reduced the cost to the client, together with associated standing time incurred from tidal delays,” said Matt Chappell, a specialist in nearshore site investigation at Fugro. Disruption to river traffic was also minimised.

“The Skate 2 proved well suited to dealing with London’s various challenges. As well as bridge transits, its ability to safely undertake ground investigation in close proximity to tunnels, river walls and heliports was extremely useful,” said Shawn Sismondi, senior geotechnical engineer for Ferrovial Agroman.

Working in challenging intertidal waters, Fugro barge masters drew on their substantial experience to achieve problem-free jack-up and preloading operations in the highly variable geology, avoiding leg penetration and punch-through risks in the challenging riverbed formations.

A total of 25 boreholes were drilled using a combination of cable percussive, rotary and directional methods to depths ranging between 25m and 79m. A programme of downhole geophysics and in situ testing provided further, high resolution geological and geotechnical data. Cone penetration testing was carried out at 19 locations, many of which used the seismic piezocone to deliver key information on geotechnical parameters.

The complex work demanded high levels of competence from the Fugro team, including geotechnical engineers trained and experienced in London Basin logging. Team members also completed Tideway’s progressive health and safety induction, EPIC, which is championing a rigorous safety culture for workers on the project.

One of the UK’s biggest civil engineering projects, the £4.2 billion Thames Tideway will incorporate 25km of tunnelling to update London’s ageing sewer system for modern needs.

Fugro has worked on numerous Thames projects, including: Garden Bridge, London Gateway, Putney-Becton Sewage Tunnel, the London Array, Canary Wharf, Royal Terrace Pier, and other current contracts at Tilbury Power Station, Tilbury Docks, and the Oikos Jetty (Canvey Island).