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Increasing the Bearing Capacity of Ilford Railway Facilities

Summary

As part of the Crossrail scheme, Ilford rail depot was subject to refurbishment and improvement works. The main issue at hand was that the current facilities original design was not suitable proposed improvements. Uretek was called to repair and upgrade foundations in an effort to withstand increased loading and improve the integrity of the foundations.

Volker Fitzpatrick was investing £50m to improve existing facilities and create ten sidings for Crossrail trains. With this in mind, the task for the Uretek team would involve enhancing the bearing capacity of the ground directly below the foundations and perimeter walls.

Objectives

Ground investigations conducted by ESG lead to a realisation that conditions were not suitable for suggested development. It was found that around 5 metres of made ground sat atop sands and clays. It was wholly believed that the foundations would be highly incapable of supporting an increased load of 350kN/m2, which would be the additional weight demanded by the refurbishment project.

Initial calculations carried out prior to any works and testing indicated that pad foundations set 9m apart would settle at 5mm. Research also implied that differential settlement between columns would be less than around 10m.

Plate load tests confirmed that the final outcome would be 2.5mm; significantly less than the presented 25mm specification.

Technology Applied

Whilst the most conventional approach, techniques such as mini piling were essentially impossible to incorporate given that disturbances in time and ownership issues meant they were unsuitable for this particular task.

It was Volker’s consultant, RPS that recommended using Uretek and our geopolymer injection solutions to effectively deal with the challenges posed by the steel frame of the building. This solution was suggested due to the fact that no excavation works would be required. This meant that works could be executed even where there was minimal access.

Geopolymer injection was used to adequately increase the bearing capacity. Two load plate trials were carried out to assess the success of the project and establish that our design could cope with the additional weight and pressure.

Outcome

The treatment itself was comprised of four 52mm diameter, 5m depth injection locations, of which two were created via vertical drilling and the other two inclined through the actual foundation. Overall, 19 pad foundations were treated at a rate of around 10 minutes per injection.

Strip footings were treated with injections at 1.5m centres along the walling for the whole of the 168m length of the building.

Four Uretek teams worked on the site simultaneously. Despite having to contend with an unfortunately compromised worksite, Uretek manage to complete the project in 10 days, completely on time. The facilities were capable of and ready to welcome the next phase of the development.