Articles & Case Studies


Posted: Friday 19th February 2010

Insituform Technologies Ltd. (ITL), a leader in the provision of rehabilitation systems for the repair of deteriorated pipelines across the globe, has developed techniques and products over the years that have a wide range of application across the international water industry. In addition to potable water and wastewater pipelines, ITL has also developed expertise in the rehabilitation of storm and surface water drainage systems, including culverts.

A recent project for client Network Rail highlighted this skill in culvert renovation. Designated the Network Rail Edale Culverts Project, the work was situated near to the town of Edale, Derbyshire, UK. Three culverts running beneath the main railway line from Sheffield to Manchester, required rehabilitation. The principal contractor for the project was Birse Rail. The design was completed by Birse Rail Consultancy.

After careful consideration of the available rehabilitation options, it was decided that the best option for the culvert renovation works would be the installation of CIPP liners, for which ITL was appointed as the installation subcontractor.

The work required extending the life of the existing rectangular stone culverts, each 800mm high and with widths that carried between 450mm to 500mm. Access to each of the sites was through farm fields comprised of grassland normally used for grazing.

ITL offers a wide variety of techniques and liner products suitable for this type of installation To ensure that the future flow performance and structural integrity were maintained at the maximum with a minimal loss of cross-sectional area within the existing culverts, it was decided to utilise a cured-in-place pipe (CIPP) lining system with pressure grouting of any remaining annulus between the new liner and the existing culvert wall.

To minimise the wall thickness of the liner and provide a high strength liner, ITL chose to install its premium CIPP product, the iPlusComposite system (detailed below). The installation technique used standard Insituform® CIPP equipment including a mobile crane. Given the location of the installation sites, Network Rail carried out bearing checks for the use of a mobile crane. This ensured that the weight of the crane would cause no problems to the site where the culverts were being renovated or to the tracks beneath which the culverts run.


The iPlus Composite design is fibre-reinforced and ideal for rehabilitating medium- to large-diameter gravity pipes from 610mm to 2,100mm.

The proprietary technology of iPlusComposite includes reinforcing fibres integrated into the pipe wall forming a laminated sandwich structure with improved physical properties. The improved flexural strength makes the iPlus Composite system an excellent material choice for non-circular cross-sections that contain straight sides (i.e. egg shapes or flat bottom arch pipes) as well as those likely to be subject to higher than usual external loadings (i.e. high long-term traffic flows, etc.).

By combining innovative engineering technology with high quality materials, iPlus Composite delivers increased flow capacity relative to the host pipe when compared with more conventional rehabilitation techniques. The product is being hailed as a next-generation CIPP system that, due to reinforcing carbon and/or glass fibres, provides a structural solution that is up to 50 percent less than the thickness of traditional pipe lining solutions. The composite material thereby maximises pipeline capacity even after lining. As with other CIPP products, the applied pipe loads are calculated according to the trenchless technology industry’s accepted standards. The new liner’s reinforcement fibres are resistant to the corrosive materials and conditions found in sewers. Carbon and fibreglass materials have excellent chemical resistance to materials found in sewers and exceed current trenchless industry corrosion requirements.

The iPlus Composite system can truly claim to be a product that does more with less. Less resin is used in the product, less energy is required to cure the product and less fuel is needed to transport the product to the jobsite. The iPlus Composite product can be installed in less time than conventional CIPP, thereby saving energy and reducing emissions released into the air from on-site equipment. All of these factors are good for the environment and help contractors meet reduced emission targets and conserve energy. The iPlus Composite system is an effective, time-saving and environmentally friendly solution.

iPlus Composite liner benefits also include:

· Provides a seamless, jointless pipe-within-a-pipe

· Restores structural integrity

· Significantly reduces infiltration

· Stabilises pipes with a wide range of shapes

iPlus Composite has a coating on the inside pipe surface. This elastomeric flow surface coating increases the pipe’s smoothness, reduces the surface friction and provides an additional corrosion barrier for the pipe.

The iPlus Composite tube is manufactured in Insituform’s ISO-certified manufacturing facilities. This ensures the tubes are made with the same attention to detail and high standards of quality that customers have come to expect.

In addition to the Company’s own testing of the iPlusComposite product, independent testing to establish the E-modulus of the cured liner material has also been carried out at Coventry University in the UK. Using three iPlus Composite samples, results of the Coventry test showed on average that the E-modulus of the product was in excess of 5,000 MPa. One of the three samples tested showed an E-modulus of over three times (3x) the industry recommended level of 2,200 MPa for this type of liner.


The lining work for culvert P9G22, which was 21m long, was completed on 26 June 2009. Installation on culvert P9G21, which was also 21m long, was completed on 30 June 2009 and the final 34m long installation for culvert P9G29 was completed on 12 July 2009. The final installation had to be completed with a night-time possession of the railway due to the proximity of the culvert location to the tracks. Work started on site at midnight on the Saturday and continued into Sunday morning. The main problem for this site was that a large tree obstructed the installation area of the final liner. It was therefore necessary to establish the mobile crane very close to the railway tracks, hence the need for the possession. Because this situation did not occur at the other installations, works were able to be undertaken during the daytime.

Access via private land was required at the location of all three culverts. Birse Rail arranged the access permissions and provided a plastic roadway to ensure minimum disturbance to the ground over which the equipment and supply vehicles had to pass.

Apart from these relatively minor obstacles, all three liner installations were completed very smoothly. Once the culvert in question was cleaned and inspected, any obstructions likely to damage or prevent the correct installation of the liner were removed. The liner was set up on the launch scaffold. The water for the inversion process was provided using a single road tanker. The water was pumped into the liner at the head of the scaffold, creating the necessary water pressure to invert the liner into the culvert. Once the inversion was completed, the inversion water was heated to the required temperature for curing by circulating it through the boiler truck. This hot water was circulated for a pre-determined time to ensure full curing of the tube.

Once curing of the tube was completed, the remaining annulus between the liner and the culvert wall was pressure grouted using cement mortar grout. This was placed using a standard high-pressure grout pump into the unavoidable annulus created by the inversion of an effectively circular liner into the rectangular culverts, particularly in the corners. The use of the pressure grout ensured that the full structural integrity of the lined culvert was maintained. This was a vital factor in the project given the rail traffic loads the culverts would experience throughout their working life.

However given that the liner was designed to fit the culvert, the grout requirement was minimal, hence the use of the basic cement grout.

For ITL, John Beech, Business Development Manager, commented: “These installations were not typical jobs because of the difficult access. We had to ensure that our crews minimised disturbance to the farmland wherever possible. The lining operations themselves went very well, although the logistics of getting materials and supplies to relatively remote locations was a challenge—particularly since once the liner was in place the project was not considered complete until the grouting had been completed. The use of the iPlus Composite liner was important because it meant we reduced the weight of the tube we had to handle on-site while providing a stronger liner than would have been possible with a standard CIPP liner material. The client received a renovated culvert with maximum flow capacity and a new long lease of life. Overall our crews did an excellent job on all three sites, much to the satisfaction of the client and the landowners.”

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