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M60, Manchester M60, Manchester M60, Manchester M60, Manchester –––– Vibro Stone & Vibro Concrete Columns Vibro Stone & Vibro Concrete Columns Vibro Stone & Vibro Concrete Columns Vibro Stone & Vibro Concrete Columns

Pennine Rig in operation on site (left), Zone Test being carried out (right)

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When main contractor Amec/Alfred McAlpine JV were awarded the contract to widen the M60 (junctions 5-8), they were faced with the need to widen a section on an embankment up to 10 metres high constructed on the Mersey valley flood plain. The natural geology comprised interbeded and discontinuous bands of alluvium and glacial sands and gravels all covered by fill and/or the embankment. Further complications arose with the A56 Chester road, the river Mersey, the Bridgewater canal and Metrolink all crossing the line of the motorway. Design and ConstructionDesign and ConstructionDesign and ConstructionDesign and Construction

Working with consultants Halcrow, Pennine devised methods to control settlement of the new section without causing stability problems to the existing road. Vibro concrete columns (VCC) were installed from existing

embankment toe levels extending outward to the toe of the new embankment; designed to work in conjunction with a load transfer platform the VCCs transferred loads to competent strata at depth.Vibro stone columns (VSC) were installed from a higher intermediate level; their purpose was to reduce the compressibility of the weak fill and alluvial soils and to improve overall stability. VCCs were installed for design loads up to 235kN/m2 with individual column lengths to 10.5 metres; the VSCs were installed to depths up to 13 metres to support loads from 125 to 235 kN/m2. The £1.4 million contract was completed in a 14 month period but due to the traffic flow and lane closure programme was carried out in tranches of different periods. Pennine’s work was completed in early 2005 and the Highways Agency expects the motorway to be fully reopened in spring 2006.