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Exeter City Council: Cycle Track Construction (civils)

Background

Exeter City Council was responsible for the upkeep of a 950m long by 3.3m wide cycle track located off Sannerville Way, Exminster; primarily used as a cycling and walking route for a local school and occasionally used by cars and tractors. However, due to traffic use and inclement weather, subsidence and rutting had occurred.

Problem

Previous remedial works to the cycle track had involved importing quarried stone to the site which was used to fill in the ruts and level out the subsiding ground. However, this was at best a temporary solution, as not long after the quarried stone was laid additional use and inclement weather caused more rutting and subsidence.

Solution

It became clear that a more permanent and environmentally friendly solution was required to remedy this problem and it was decided that the sub-base of the cycle track would be stabilised using the SMR proprietary binder in situ.

SMR (UK) appointed European Aggregate Recycling to use traditional stabilisation equipment and methods dig out and reconstitute the required single layer of stabilised material. Exeter City Council’s appointed contractor provided a tracked vehicle to load the SMR proprietary binder into a stabilisation hopper and they then levelled and compacted the SMR mixed material before completed the job by applying the wearing course.

Benefits

Reduced Lorry Movements: Carrying out the process in-situ meant lorry movements on and off the site were minimised compared traditional methods. Only one machine was needed to mix the SMR proprietary binder into the existing cycle track. Traditional methods would have required excavating the whole track, transporting the estimated 1400+ tonnes off site, (most likely to landfill), with a similar volume of primary aggregate then being been imported back on site to construct the new sub-base of the cycle track. (An estimated 144 lorry movements / with just eight needed for the SMR based solution). After this the primary aggregate would then be levelled/graded and compacted to produce the new sub-base for the track.

Reduced Job Time: Removing the need to transport any excavated material off site and import primary aggregate in its place, significantly reduced the job time. Traditional methods would have also seen the imported primary aggregate deposited in a storage/lay down area and then transported to the area of the cycle track where it was intended to be used resulting in double handling and additional on-site movements.

100% recovery rate achieved: With the SMR solution all material in the cycle track was re-used and converted into a stabilised material; used as the sub-base layer of the cycle track. This resulted in zero material being sent to landfill and zero use of primary aggregates. Going the SMR route meant that only a day and a half was needed to complete the sub-base element of the project, compared to the two Weeks (10 days) traditional methods would have taken to complete to the same stage.

Higher load bearing performance achieved: The Stabilised Sub-Base layer constructed using the SMR proprietary binder achieved high load bearing capabilities of 5N/mm2 which is far higher than that which would have been achieved using primary aggregates.

Social Disruption: The cycle track is accessed via Sannerville Way (A379) and is a heavily trafficked road. By using the in-situ stabilisation technique with SMR the amount of lorry movements was minimal and therefore the disruption to motorists on Sannerville Way were minimised, completing the project in a shorter time which was advantageous to the local community.