Reducing sound and vibration with high density concrete | LKAB Minerals
Floating track slab concrete london underground tunnel

In 2017, a high density Floating Track Slab (FTS) was installed as part of the Crossrail C610 project, designed to reduce the impact of noise and vibration caused by trains.

The Floating Track Slab, installed beneath the Barbican and Soho, is a known system already in use in Europe. However, use of a high density concrete, produced with the natural aggregate MagnaDense, is the first of its kind.

Space restrictions

Due to the volume constraints of the tunnel, surrounding infrastructure and gauge of the train, space was limited. The solution was to develop an FTS with a target density of 3.6 tonnes per cubic metre, limiting ground-borne noise and vibration.

Concrete design

The high density Floating Track Slab sections at Tottenham Court Road and Farrington required 4,400 cubic metres of concrete with a density of 3.6 tonnes per cubic metre. With the track situated more than thirty metres below the surface, they pumped the concrete up to 1,000 metres into the tunnel network; a world record for pumping heavy weight concrete. At its peak, the pipeline held 12.3 square metres or 44 tonnes of material.

Pumping was performed at three locations; Bond Street, Fisher Street and The Barbican, with a total of 70 night pours achieved during the project. London Concrete, working alongside LKAB Minerals, developed a flowable concrete with an open life of 4-5 hours. This specification meets the stringent requirements of such a complex project.

Logistics; both long and short distance challenges

The logistics of supplying the just-in-time deliveries of large quantities of heavy aggregate to the centre of London were far from simple. We had to make sure the material arrived at the batching plant on time and as cost-effectively as possible.

The Crossrail Project

Crossrail is one of the largest infrastructure projects of its kind. The project has seen the installation of 42km of tunnels, the building of 10 new stations and improvements to 30 more. The finished railway, which they will rename the Elizabeth line when it opens in central London, will be a fully accessible route of 40 stations from Reading and Heathrow in the west to Shenfield and Abbey Wood in the east. The fully operational railway will add 10% to London’s rail capacity, reduce journey times and improve accessibility.

The C610 project was nominated at the New Civil Engineer Tunnelling Awards and Concrete Society Awards in 2017 & 2018.

Technical webinar

In 2017, the project team provided an in-depth technical insight into the project. They did so via a webinar held in conjunction with the Institution of Civil Engineers. During this online session, they run the project from its inception & design to concrete production & installation. You can watch a replay of this webinar online.