maxit LWA Geotechnical Fill
Rail Infrastructure
Harthope Viaduct, Moffat maxit fills void to keep project on track CONTRACTORS seeking an urgent solution when large voids were found within the structure of a landmark railway viaduct, turned to a lightweight geotechnical fill from maxit UK. The unexpected voids were discovered behind the abutments of a Victorian bridge during major £8 million replacement work at Harthope Viaduct on the West Coast Main Line near Moffat. With only five days remaining before possession, contractors Skanska UK Civil Engineering of Doncaster, working on behalf of Network Rail West Coast Main Line, had to source and install a lightweight product capable of filling the voids without imposing undue loadings on the existing bridge abutments in just two days. They also required a material that could be easily “delivered” 12 metres vertically and placed in the voids, which had been caused by the gradual collapse of stone arch covers constructed behind the abutments of the original 1848 structure. maxit LWA lightweight aggregate met each of the criteria and at an assumed unit weight of 5 kN/m3 came well within the requirement specified by the Client’s consulting engineers Scott Wilson Rail, of Glasgow, for a material of less than 12 kN/m3. It also provided a number of additional benefits.
maxit Building Products Ltd. The Heath, Runcorn Cheshire WA7 4QX Tel: +44 (0)1928 515656 Fax: +44 (0)1928 576792 Web: www.maxit-uk.co.uk Email: sales@maxit-uk.co.uk
By using maxit’s 55 m3 blowing vehicle, Skanska were able to deliver the material pneumatically from ground level to the top of the old viaduct abutment, placing a full load of 10-20 mm grade LWA to fill five voids up to 10 metres in depth and up to 1.5 metres wide in a single day, allowing work on the main project to continue
alongside, limiting delays to a minimum. The use of maxit LWA meant that there was no requirement for stockpiles of material on site, no waste and no need to compact the fill. Comments Skanska design manager Spencer Williams: “Additional unexpected voids were discovered on site very late in the programme. We chose to use maxit LWA because it could be delivered pneumatically to the top of the 12 metre high abutment with minimal disruption to the site operations, and the 10 metre deep voids were filled within a single visit.” The main contract on Harthope Viaduct, a wellknown structure known locally as the “hole in the wall”, involved the replacement of the 100 metre long, six span structure that carried the West Coast Mainline to Glasgow. The project involved completely replacing the bridge – which originally dated back to 1848 and 1875 -- including construction of a new central pier, conversion to two spans, strengthening of existing support structures and piling work. Skanska slid the new 18 m superstructure into place during a planned 5-day blockade of the line.
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