The extension of the Manchester Metrolink tramway to Manchester Airport relies heavily on the load bearing qualities of Leca® Lightweight Expanded Clay Aggregate to provide a strong, stable support for the tram stop where it passes over water courses, unstable alluvium and reclaimed land.
The 14.5km (9 miles) extension creates a new public transport corridor for the western side of South Manchester; between the A56 Chester Road from Altrincham and the A5103 Princess Parkway. Linking central Manchester, Old Trafford, Chorlton, Wythenshawe and Manchester Airport; greatly improving access to areas south of the River Mersey. Leca® Lightweight Expanded Clay Aggregate was specified for use on three of the projects within this major new transport investment.
A trackway span was built over the Chorlton Platt Gore water course which required excavating the existing bank of the brook to allow for the construction. Using traditional materials over the underlying alluvium and unstable ground would have led to differential settlement between the solid structure and the embankment resulting in a three month predicted delay for consolidation. To accelerate the programme and alleviate this potential delay, Leca® Lightweight Expanded Clay Aggregate was used to backfill the structure and overcome the requirement.
The new Hardy Farm Stop and embankment are constructed over the eastern flood plain of the River Mersey. Leca® Lightweight Expanded Clay Aggregate was selected to minimise the size of the piled foundation slab and mitigate effects of long term differential settlement of the embankment supporting the track bed over a large area of alluvium and made-ground to provide sufficient width for the new tram line and platforms.
A concrete piled ‘L’ shaped platform/retaining wall and a reinforced concrete piled ‘U’ trough supports the Metrolink embankment at the south approach to the M60 motorway. To the end of the retaining structure the embankment is un-retained to return to grade. The embankment runs adjacent to and crosses over a 3rd party sewer which required a limitation of 25mm settlement. The lightweight attributes of Leca® Lightweight Expanded Clay Aggregate were called upon to eliminate the risk of over- burden on both the pipe and the existing embankment stability.
A totally natural product, Leca® Lightweight Expanded Clay Aggregate is formed by heating and firing natural glacial clay in a rotary kiln at temperatures up to 1150ᴼC. This process transforms the clay into lightweight ceramic granules with a hard shell and porous core. With a bulk density of just 0.3 tonnes per cubic metre,Leca® Lightweight Expanded Clay Aggregate has excellent insulation properties, is free draining, fire resistant, frost resistant and chemically inert with no hazardous properties. Used as a lightweight aggregate fill in many civil engineering and construction applications Leca® Lightweight Expanded Clay Aggregate reduces the weight on weak substrates and against retaining structures by up to 75% over traditional fill and eliminates expensive settlement delays, is easily handled and quickly installed.
The main contractor for the civil engineering work in this major design and build project is M-Pact, the joint venture operation between Laing O’Rourke and Volker Rail. James Oliver, Project Manager for Laing O’Rourke, was very positive on the values of Leca® Lightweight Expanded Clay Aggregate. “We carried out a commercial cost assessment of the materials available and proposed Leca® Lightweight Expanded Clay Aggregate at the design stage. It proved very practical to place into position, easy to compact accurately and overall easy to handle. A sterling job was done on the logistics which is always variable on a project of this magnitude and is affected by weather and related construction timings but the Leca® Lightweight Expanded Clay Aggregate team worked with us excellently to get material to site on-time even at short notice.”