Network Rail – Geotechnical and Structural Investigations

Project Summary

Soil Engineering was appointed by Network Rail to carry out structural and geotechnical investigation at London Bridge Station.
Part of the investigation required sample positions to be formed through the station platform.

Restrictions

To access these positions it was necessary to track the investigation plant and machinery through the station and across the platform. However, the platform was suspended in places and as a consequent could only withstand limited weight upon it.

The void beneath the platform did not provide sufficient head room to form sample holes below the platform using light weight, hand held equipment. The specified sampling regime required the use of a Terrier rig, however, the plant and equipment was too heavy to be tracked across the platform and to further compound the problem, the pull down pressures anticipated during drilling and sampling were too great to form the boreholes through the platform.

Soil Engineering Solution

A series of temporary works solution was designed and constructed below the suspended station platform. The props were aligned with proposed access routes as well as sampling positions.

The surface area beneath the platform cleared and levelled using sand to ensure an even spread of weight. The props comprised structural timbers and were supported using two weight bearing acro props and a central load beam.

The temporary works were designed with the help of VINCI Construction UK Limited and approved by Network Rail engineering staff who deemed them safe and suitable for the proposed works.

Value

All of the materials for the temporary works were delivered below the platform and constructed during night shifts. The temporary works were easily and quickly installed to allow timely progress of the investigation.

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