Saturday, April 13, 2024

ILine GRP Lining Restores Brick-Arch Culvert

With what is claimed to be unrivalled installation experience, including a full design service, iLine offers numerous services and products to all its clients.

When a structure is in danger of collapse and needs its structural integrity restoring with minimal disruption then iLine Technologies has a range of rehabilitation solutions to suit most situations. With what is claimed to be unrivalled installation experience, including a full design service, iLine offers numerous services and products to all its clients.

The Old Victoria Culvert is a single span brick-arch with a concrete extension carrying a tributary of the River Lark beneath the single carriageway A134 (Sudbury Road) and private gardens located between Sicklesmere and Great Whelnetham in Suffolk, UK. As with many old brick-arch culverts it has differing cross sectional areas with a width of 1.72 m x 1.07 m high for the first 34 m including 6 bends, which then changes from the flat bottom brick-arch into a 1.2 m diameter circular concrete pipe for the last 10 m. The overall length of the culvert is 44 m.

Repairs to brick-arch had previously been carried out, however, the concrete pipes had significant cracks in the crown and were badly deformed which was caused by settlement of the pipes and there was evidence of scour to the invert. Overall, the structure was considered in danger of possible collapse. Suffolk Highways and its framework contractor, Kier Infrastructure Services, approached iLine to discuss potential solutions to restore the structural integrity of the culvert. Because of the varying sizes, transition from one shape and size to another and the presence of bends, GRP prefabricated units were chosen as the best and most cost-effective solution.

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Working with Suffolk County Council (SCC) structural engineers, an initial WRc Type 1 structural design was undertaken by iLine and Channeline International, the supplier of the GRP units, to enable the units to carry loads in accordance with LM1 of the BS EN-1991-2- 2003 Eurocode 1-traffic loadings on bridges.

Bespoke purpose-made units were designed to accommodate not only the 6 bends but the transition from 1.72 m x 0.875 m flat bottom brick-arch, into the 1.2 m circular concrete pipes for the last 10 m. Specialist point cloud and topographical surveys were commissioned to confirm an accurate shape and profile of the original culvert to enable confirmation of the GRP units shape and sizes.

Following discussions with the SCC flood team to ensure maximum flood capacity, it was agreed to lower the invert in the arch section by digging out the soft silt and gravel to enable a larger liner to be installed achieving a greater storage capacity. Flow calculations confirmed that due to the manning coefficient of friction an increase of 110% of the original capacity was achieved.

After further discussions and site investigation work, it was decided to manufacture shorter GRP sections to enable all the arch shape units including the transition piece to be installed from the inlet ends so that they could easily pass through the 6 bends. A double collar transition piece was designed to allow installation both up-stream and down-stream from this point. The circular units were installed from the downstream end up to the transition piece. Some 34 m of flat bottom GRP arch shape units 1.5 m x 0.875 m x 26 mm thick and 10 m of circular GRP units 1.0 m diameter X 17 mm thick including 6 bends panels and a double collar transition piece were all manufactured and shipped from the Middle East by Channeline International.

iLine’s experienced installation team then completed the installation works to the satisfaction of both the client and residents. An initial road closure was required for a week of night shifts to clean and dam off the flows through the original culvert to allow installation of the new GRP units.

During cleaning of the culvert, soft spots were discovered along the line of the brick arch section. These required full removal and a firm base was installed. The GRP units were then installed from both the inlet and downstream end. Grouting between the newly installed GRP units and the Host structures was completed on site using 12 N/mm2 cementitious materials. This work was carried during the day under a 2-way traffic light system. Despite the additional works, the project was completed within the prescribed timescale of 8 days to the satisfaction of all parties involved, with minimal disruption to both the residents and local traffic.

This was an exceedingly difficult and complex rehabilitation job which was completed by iLine with minimal fuss and to the satisfaction of all.

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