The Midland Main Line passes through some relatively hilly areas of which Sharnbrook in Bedfordshire is one. Within this region, there is a 1 in 119 gradient from the south taking the line to 100 metres (340 feet) above sea level.
Following a number of embankment slips along a particular stretch of the line, a need was identified for a series of three retaining walls ranging along a total stretch of some 262 linear metres.
As the lead design consultant for the project, Corus Rail Consultancy reviewed the options available and designed and specified a series of mass gravity gabion walls as the preferred retention element. The key challenge was to construct aesthetically pleasing structures in this environmentally sensitive rural location and to ensure that these would withstand the dynamic forces from the imposed loadings – from above and behind.
Commercially, the investment in the gabion wall construction needed to fall within a pre-determined budget and be manufactured to suit the timings of the site construction programme for the main contractor, May Gurney Limited.