Successful Application Of Mixed Abutment Construction To A Freight Rail Foundation On Granular Soil

The abutment structures for the Glenfield Flyover on the Southern Sydney Freight Line (SSFL) present an interesting application of mixed abutment construction using the Reinforced Earth System. The abutments support a long deck that spans over the Main South Line (MSL) tracks that run under the flyover. The abutments are not only to retain the embankment on either side of the MSL but also to support the deck structure. The abutment structures are long because of the geometry of the flyover, with a crossing angle of 15˚. The foundation conditions are of loose sand with minor clay layers that overly rock at about 11 m depth. Conventional concrete retaining wall construction would require large diameter piles or an equally expensive equivalent constructed from raked and vertical driven piles. An advantageous alternative is to adopt a mixed abutment, which has a piled frame to support the flyover deck with the Reinforced Earth construction to retain the embankment and protect the frame columns from collapse under accidental impact from railway traffic. The Reinforced Earth foundation can be constructed to provide a wide footing to suit the ground conditions of relatively deep sands.