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Ground improvement for railway arch renovation


The project involved the ground improvement of four arches which were being converted into office storage spaces. The specific challenge at the site was addressing the inadequate foundation of walls that were initially constructed to block off the archways from neighbouring gardens. These walls, built directly on the soil with minimal foundational support, required reinforcement to support the planned conversion into functional units.

injection tubes

Injection tubes in place


  • Inadequate Foundations: The walls backing onto neighbouring gardens were constructed with little to no foundational support, raising concerns about their stability and the feasibility of the planned renovations.
  • Project Location: Located in the heart of London, the site presented typical urban challenges, including limited access and the need to minimize disruption in a densely populated area.
  • Soil Composition: The ground beneath the arches consisted of London clay, known for its potential to be quite soft, which could compromise the stability of the structures above it.


Geobear was contracted to implement a ground improvement solution beneath the existing wall foundations. The approach involved injecting a geopolymer into three levels below the foundations at specific intervals to enhance the soil’s bearing capacity. This method was chosen for its minimal intrusiveness and its ability to quickly stabilise the foundations without the need for extensive excavation or demolition.


One alternative to the chosen solution was the complete removal of the existing walls and the construction of new foundations. However, this approach was deemed too intrusive and time-consuming compared to the geopolymer injection method.

Tubes removed

Tubes removed grouted

Benefits of Geobear approach

  • Enhanced Stability: The injection of geopolymer significantly improved the bearing capacity of the soil beneath the arches, increasing it by up to 200% in some areas. This enhancement ensured the long-term stability of the renovated arches.
  • Quick Implementation: The entire project was completed within three days, demonstrating the efficiency of the geopolymer injection method.
  • Minimal Disruption: By opting for an injection-based solution, the project team minimised the disruption to the properties backing onto the arches.


The ground improvement project at Castle News showcases an innovative approach to addressing the foundational challenges of renovating historic structures. By utilising geopolymer injection, the team was able to quickly and effectively enhance the soil’s bearing capacity, ensuring the stability of the arches for their future use as office and storage spaces. This case study demonstrates the potential for modern engineering solutions to overcome the limitations of existing infrastructure, even in challenging urban environments.

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