Platform Extension - West Hampstead Railway Station

Leca® LWA makes lightweight, high-speed, extensions

Over 940m³ of Leca® LWA was supplied for the width and length extensions of three high-traffic railway platforms at West Hampstead station in London. Leca® LWA is a lightweight, expanded clay formed by heating and firing natural glacial clay. Ease of handling and its ability to be blown into position by the Leca® UK combined vehicle and blowing unit avoided access problems and lengthy settlement delays. The 10 - 20mm aggregate, specified by Network Rail, was delivered loose-tipped to site and blown pneumatically into place by the specially adapted vehicle. The mechanical action reduced manual handling to a minimum which contributed greatly to a reduction in on-site man hours and labour costs. Widening of other existing platforms was then carried out manually in voids running the entire length of the platform. A basic geotextile membrane was first laid between the fill and the underlying soil to avoid migration of fines. Then the material was blown into the extended platforms adjacent to the retaining walls. The lightweight Leca® LWA was spread to a depth of 600mm and compacted with 3 - 4 passes of a vibrating plate compactor. Some 16 x 60m³ deliveries were made to this difficult access location compared with almost 80 loads of traditional hardcore material, reducing both transport costs and the associated environmental impact. Danny Marshall, Contracts Manager for Walker Construction working on behalf of main contractor Carillion PLC, said: “This was a complex project by Network Rail and speed of application was paramount to avoid passenger disruption and to reduce installation costs. A 4” steel pipe line was installed to feed the Leca® LWA beneath the railway tracks which allowed the job to be carried out in normal working hours while the trains were operational. In all, the work was completed in 6-7 days, a fraction of the time that it would have taken if traditional fill methods had been used.”