Network Rail – Polystyrene Platforms

Project Summary

Soil Engineering was appointed by Network Rail to carry out a structural and geotechnical investigation at London Bridge Station.  A number of deep trial pits were due to be dug to investigate the structure of the arches located below the area of the Rail Track structure.


There was insufficient possession periods available to allow the movement of railway infrastructure and the construction of the trial pits. Access was restricted to night time or weekend possessions and the work area had to be cleared at the end of each shift. An alternative solution had to be found.

Soil Engineering proposed the use of window sampling equipment to gain the information. The position of the investigation points remained the same, in the “Four Foot” between the electrified tracks adjacent to the platform of the operation station. However, due to weight restrictions on the platforms it was not possible to use lifting equipment to lift the terrier rig and sampling equipment directly onto the tracks.

Soil Engineering Solution

High density foam slabs were used to construct a working platform over the rail tracks. The area to be investigated was first levelled using ballast. The polystyrene blocks were laid directly onto the ballast, bridging the tracks, and then built up to be level with the station platform.

The polystyrene blocks were of sufficient density to safely support the front end of the Terrier rig and its operating personnel.

A safety rail was constructed of timber of suitable quality and dimension around three sides of the platform leaving only the access from the platform open. The safely barrier comprised hand rails, corner bracing and struts on all three sides.

The barrier and platform system was approved by Network Rail engineering staff who deemed it safe and suitable for the proposed works.

All the platform and safety barrier equipment were hand carried across the station platform at the start and end of each shift. The system was easily and quickly assembled ready for use. The terrier rig and equipment were tracked across the station platform directly onto position.

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