11-10-2006
14/11/2006
A housing development site overlooking the picturesque Firth of Forth has become the first mainland UK, major project to use the innovative, Landmark Segmental Retaining Wall System from Anchor Wall Systems [AWS]
The steeply sloping brown-field site, until recently a redundant bauxite processing plant, was acquired by Scottish developer, Stewart Milne Homes and will eventually provide 100 detached houses for the town of Burntisland in Fife
Re-contouring of the site to create level building pads for the new houses and to allow maximum use of the available land meant that retaining walls were required to form bold terraces up to 6.0m in height.
As one wall was required within 9.0m of a main highway, the more conventional retaining wall solutions had to be rejected in favour of Anchor Landmark Segmental Retaining Wall System. It is a requirement of The Highways Agency and Scottish Executive that soil retaining structures constructed close to or as part of a major highway must comply with key performance criteria of strength, durability and long design life.
Anchor Landmark carries British Board of Agrement [BBA], Roads and Bridges Certification making it the ideal solution in this challenging application Allan Rice of Engineers Maccaferri, who designed and built the wall explained. We considered a variety of solutions but Landmark gave us the assurance of a proven system with a design life of 120 years. It helped us convince the Highways Authorities that this type of retaining wall was right for the job
Anchor Landmark, Segmental Retaining Walls are different from other systems because they incorporate what the industry describe as a “positive connectivity” device that locks the two principal components together – concrete facing blocks and polymeric geogrids.
Positive connectivity gives the system immense strength, preventing pullout of the geogrid under load and enhancing the stability and earth retaining capability of the system. With such a high structure at the Stewart Milne Homes site, it was essential that a proven system was selected. Reassuringly, Landmark Walls of over 20 metres in height have been constructed in America, where the technology was developed.
Most segmental retaining wall systems rely on the friction created by the weight of subsequent courses of concrete facing blocks to prevent pullout of the geogrid. The geogrid itself is sandwiched between the blocks and laid out horizontally behind the wall, binding with layers of compacted backfill to create a stable, mass, earth retaining structure.
Anchor Wall Systems’ Landmark blocks are different in that they incorporate a lower locating flange and a corresponding receiving channel on the upper face of each facing block. During wall construction, the geogrid is placed into the receiving channel of the previously laid course of blocks and held in position by a PVC locking bar. The lower locating flange of the subsequent course fits into the channel and prevents rotation of the locking bar and pullout of the geogrid, creating the “Positive Connectivity” feature which gives the system its high level of performance.
The Stewart Milne Homes development at Burntisland is the first significant Landmark application in the UK mainland. Over 700m2 of wall were installed in a single structure, 168m long and 6.0m high at its maximum. The system’s green credentials are also highlighted as exclusively site-won backfill was used to construct the wall, eliminating the need for almost 600 heavy vehicle journeys to and from the site.
Three additional Anchor retaining walls totalling over 950m2 were built at the site using the Company’s Vertica System.
Anchor Retaining Wall Systems are marketed in the UK in partnership with concrete products manufacturer, Acheson & Glover Group and Maccaferri, who provide engineering and technical support.
