Page 36: of Offshore Engineer Magazine (Mar/Apr 2015)

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EPIC

Getting to grips with grout

Grout is taking on new forms to meet the needs of ofshore wind applications, Jim Bell explains. rout is fundamental for offshore structures, for member flling to

G strengthen and repair jackets; fabric formworks to support and stabilize pipelines and grouted clamps to repair damaged pipelines or jackets.

FoundOcean’s RJM (recirculating jet mixer).

Although only contributing to a small proportion of a project’s costs, in the case of foundation installation, grout is an essential component which contributes to the structural integrity of the foundation and therefore its long-term capacity to generate revenue. As such, it is essential to choose the best material for the job.

Grouts for offshore use come in a number of different strengths; standard, high and ultra-high. However, strength is not the only material property that needs to be considered; durability and volume stability also need to fgure highly. The

FoundOcean worked on the 30 wind turbine Ormonde Ofshore Wind Farm, 10km potential for improving project productiv- hand, have numerous applications in of Barrow-In-Furness in the Irish Sea. The farm used jacket foundations similar to those used for oil and gas platforms. Ormonde was the frst large-scale commercial ity rates and safety, both on and offshore, situations that require 28-day characteris- wind farm in European waters to use jackets for the turbine foundations as well as linked to the mixing and pumping, tic strengths of 100MPa or higher. These the substation foundations. Photos from FoundOcean.

delivery and resupply, and storage of the types of grout are synonymous with material are also very important. monopile transition pieces for offshore

Oil and gas addition to bending and torsion. Pile The supporting foundation structures wind foundations. Ultra-high strength

Foundation design for greenfeld oil and sleeve grouted connections however will for offshore wind turbines are typically grouts are occasionally used in life gas structures very rarely demand ultra- be subjected to simpler loading consist- either monopiles with transition pieces, in extension projects where they are used strong bonds; ordinary Portland cement ing of compression and tensile forces. shallow water depths up to 35m, or four- to replace OPC in member strengthening (OPC) is therefore most often used, provid-

For these reasons, high strength grouts legged jacket structures for deeper waters. projects and in grouted repair clamps. ing a connection that is more than ade- Ultra-high strength grouts have

The loads acting on both types of struc- are required for monopile/transition quate. OPC is suitable for projects specify- enhanced properties over OPC, which have tures would be similar and would involve piece connections, in order to resist the ing strengths of between 40 and 70MPa; for been engineered into the product to allow the following; wind loading, wave loads, extreme loading conditions that apply. example, in main leg or skirt pile grouting for the dynamic loads and choice of foun- current, boat impact and fatigue loads In a typical monopile/transition piece of platforms or in the flling FoundOcean’s dation. For grouted connections in offshore (low stress, high cycle wave loads). connection, with a monopile of 5.8m fabric formworks. This tried and tested wind, FoundOcean primarily uses BASF

As monopiles are stand-alone single upper diameter and 7.8m lower diameter, practice of offshore grouting with OPC is MasterFlow 9500, for which it is a licensed structures, the monopile/transition piece the grouted connection would require carried out by FoundOcean using its recir- applicator. MasterFlow 9500, in addition grouted connection is subjected to very approximately 20.0cu m of high strength culating jet mixer (RJM), which achieves to ultra-high strength, offers a number of different loading conditions when com- grout, such as MasterFlow 9500. mixing rates of up to 30cu m/hr. pioneering properties, including; pared to the pile sleeve grouted connec- For pile sleeve grouted connections • where OPC is typically used, a single tions of jacket structures. The monopile/ Zero autogenous shrinkage, a factor

Ofshore wind connection may require up to 8.0cu m of transition piece grout will be subjected that has been shown to cause cracking

Ultra-high strength grouts, on the other ordinary Portland cement (OPC) grout. to compression and tensile loading, in in high strength concrete structures and

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