An attractive Victorian retaining brick wall has been in place for nearly 100 years in Sparth Bottoms Road.
Leca® LWA helps save a piece of history
An attractive Victorian retaining brick wall has been in place for nearly 100 years in Sparth Bottoms Road. The 144m run of walling varies in height along its length up to a maximum of 5.5m. The wall supports a pavement serving two blocks of terraced houses and accommodates numerous services including gas and water. The wall is also crossed in two places by sewage pipes. It is thought that over time, the weight of the traditional back fill, mostly sand and gravel, coupled with dysfunctional drainage, resulted in excessive pressure on the back of the wall, which then caused overturning of the masonry retaining wall. Further movement could have put the properties adjacent to the top of the wall at risk.
Remedial work was required by the Impact Partnership, an innovative joint venture company between Mouchel Group, Agilisys and Rochdale Metropolitan Borough Council, who specified the use of lightweight Leca® LWA 10-20mm aggregate as the ideal material to replace the traditional backfill. Impact Partnership delivers highways, property and ICT services to support the regeneration of the Borough.
The principal contractor, A.E. Yates Limited, of Bolton, excavated to a depth of two metres behind the retaining wall into the existing backfill which was then replaced along the entire length of the wall with 650m³ of Leca® LWA. The retaining wall also had a reinforced concrete toe constructed to the front and was extensively cleared and pointed before being finished off with a new pedestrian guard rail to the top of the structure. Leca® LWA is an expanded clay formed by heating and firing natural glacial clay at up to 1150°C. This process transforms the clay into lightweight ceramic granules that have a hardshell and porous core. The material is extremely light with a bulk density of just 0.3 tonnes per cubic metre. It was delivered to site on 60m³ tippers and stored during the construction process to enable continuity of work.
Jonathan Parker, of A.E. Yates Limited, said: “I’m impressed. This product is easy and clean to use and has allowed us to work to the 16-week programme which would have taken far longer had we replaced the original backfill material like for like and of course we would have incurred compaction issues. Leca® LWA overcomes settlement periods and reduces the number of site deliveries of the material which makes this a very environmentally friendly solution. We have covered the material with a basic geotextile membrane and type 1 subbase ready for finishing. There has been minimal disruption for the residents of Sparth Bottoms Road and this Victorian edifice is now safe, sound and in good condition.”
Alan Lowe, senior engineer, Impact Partnership, said: “I am very satisfied with the performance of this material because of its quick and easy placement, particularly when working around existing services and in the confined working space we have on this scheme.”