Inspecting and maintaining railway covers in Liverpool
Between Liverpool Lime Street and Edge Hill railway stations are several covers that cut onto the University of Liverpool campus and need continual maintenance. To provide long-term services inspecting and monitoring the integrity of the covers, the university contracted RSK’s Materials and Structures team.
The covers consist of a series of prestressed, high-alumina-cement, I-section beams that were constructed in the early 1960s. They span the trackbed, and in a wet and humid environment the cement undergoes changes to its composition over time, due to hydration. These changes make the covers prone to a loss of strength and susceptible to chemical attack and reduce their resistance to corrosion from embedded wires. These issues are obviously a major concern for both the university and the railway.
In 1995, initial materials sampling and inspections were carried out. Fifteen years later, RSK conducted a comprehensive inspection and assessment of the entire range of covers to provide a benchmark evaluation against which to measure future inspection and sampling results. The evaluation included a visual condition survey, materials sampling, chemical testing and petrographic analysis. These were done in order to identify any ongoing harmful processes; to determine concrete strength and residual prestress; and to inform the structural assessment of the beams.
Since the initial inspection and assessment, RSK has continued its oversight and stewardship of this sensitive asset. This includes liaising with Network Rail for tunnel access within short working windows and providing regular inspections and concrete repair work. For work on top of the covers, we have drafted waterproofing repair specifications and have provided contract administration and on-site supervision for contractors removing and reinstating the waterproofing.
As a part of the ongoing project we are also collecting condition information data to create a service life assessment plan for the university and Network Rail. Our success and ongoing work on this project depend on the combined experience and efforts of our expert project managers and certified inspection engineers.