THE PROBLEM
The existing track was deteriorating due to weak variable subgrade below the ballast layer combined with a high ground water level. Improving track quality was necessary to meet the performance parameters of a European corridor railway line.
THE SOLUTION
The poor subgrade was removed and the track reconstructed using recycled ballast as a sub-ballast. The performance of this layer was enhanced by mechanical stabilisation using Tensar TriAx TX190L.
PROJECT DESCRIPTION
Complete reconstruction of the railway structure situated on European corridor line I, raising the design speed to 160km/h.
The existing poor quality subgrade was excavated. By adopting Tensar Technology, it was possible to significantly reduce the excavation depth by incorporating a mechanically stabilised sub-ballast layer. This was a major benefit to the project as there was a high water table in the area. In some sections, two layers of TriAx TX190L geogrid were utilised to further increase the sub-ballast stiffness.
The use of TX190L contributed towards significant construction cost savings for the client as it was possible to use recycled ballast as fill material for sub–ballast stabilisation. The large apertures of TX190L were compatible with the recycled ballast, creating a positive interlock.
For this project a geotextile layer was also incorporated to provide a separation function preventing the fine subgrade particles from contaminating the MSL. This was considered beneficial due to the open graded aggregate used for sub-ballast, and the presence of the high water table.
