Passenger volumes on the South London main line network in Balham have been excessive for many years and predicted to continue growing as the Capital continues to offer substantial employment opportunities. With Network Rail’s implementation of their Route Utilisation Plan (RUS) to improve train capacity and the related infrastructure, the core element was to increase the length of the trains from 8-cars to 12-cars thus adding more passenger capacity.
Lengthening the trains demanded the corresponding extension of platforms to facilitate safe passenger traffic. A programme of station expansion was scheduled and Balham station in South London is an example of the work carried out.
The sites and structure of these older stations and the close proximity to both domestic and commercial premises is a constant pressure when designing and constructing the extensions. Access in many instances is greatly restricted. At Balham the platform extension design was provided by consulting engineers Cass Hayward with VolkerFitzpatrick appointed as the main contractor. Works included major alterations to the station, improved access, ticket hall and passenger facilities.
Andy White of Cass Hayward explained that the Balham platform extension required a new wall structure to act as an abutment to carry the load from the bridge deck and as the embankment retaining wall. The tight confines of the new structure left a narrow gap where the weight of traditional fill would not have met the 120-year design life criteria, the lightweight and free draining attributes of Leca® Lightweight Expanded Clay Aggregate meant that the fill requirements to this narrow gap were achieved. The choice of Leca® Lightweight Expanded Clay Aggregate also meant that the material could be blown through a pipe-work system direct from the pneumatic delivery truck into the gap. A total of 85m³ of Leca® Lightweight Expanded Clay Aggregate was installed and capped with 600mm of 6N.
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.
Martin Bradley, project manager for VolkerFitzpatrick, was impressed with the speed of placement. “I have used Leca® Lightweight Expanded Clay Aggregate previously but the blower system really made this job easy.” Sword Contracts was responsible for the fill placement and Jimmy Goodwin-Sword of Sword Contracts supervised the operation. “We made certain that the site was completely ready and ran 25 metres of pipes from the blower truck over a 4m high retaining wall.It took us just 4 hours to place the fill with the minimum of compaction. The speed of this job really helped us meet the target dates."