Structural Soils, an RSK Group company, said overwater boreholes formed part of the investigation work with the team operating through an 11m water column before cable and rotary drilling operations could be undertaken to 45m with the company's new high-pressure dilatometer capability testing forming part of this work.

It was crucial for the team to plan and coordinate our mobilisation and operations precisely

Senior engineering project manager Gareth Jones said: "The team is accustomed to overwater work and so the marine environment is not new to us. In this instance, however, we worked from the deck of an 18m x 18m jack-up barge with both a Dando 2500 cable rig combined with a rotary MC450P rig of 9000kg gross weight and a mast height of 6.2m. With limited space available to us on the deck, it was crucial for the team to plan and coordinate our mobilisation and operations precisely.

"The project also required piezocone penetrometer tests (pCPT) to determine soil type and conditions and land-based trial pits were undertaken to help the client understand surface soil conditions and to assess the dock wall structural arrangement."

Jones added that one borehole presented positive artesian water pressure, forcing soils up the drill string which required Structural Soils to mobilise additional equipment to the site and alter the drilling technique, using a thick polymer mud to advance the borehole.

The jack-up barge legs, which reached 20m in height, required the team to coordinate its work with the London Airport flight schedule to ensure barge movements did not disrupt air traffic.

The work for Lendlease, as part of The Silvertown Partnership project, also involved ground investigation work using cable percussion and rotary coring along with laboratory and in-situ testing.

RSK Safeground carried out the ground penetrating radar (GPR) for the land-based trial pits with another RSK company, Envirolabs, undertaking geo-environmental testing.

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