A combination of spray-applied membrane and sheet membrane enhances the best features of both systems
The design of the sprayed concrete tunnel linings for Crossrail typically has a spray-applied waterproofing membrane between two layers of permanent sprayed concrete.
At Farringdon Station, BFK JV adopted the use of TamSeal 800 spray membranes for the higher-level escalator and ventilation shafts as they were driven in the London Clay formation.
The structures on the West side of London were constructed through sandy clays, and the risk of higher water ingress in the lower-level tunnels steered the design towards conventional PVC sheet membranes.
TamSeal 800 spray-applied waterproofing membrane was selected as the best solution by the JV team for the sections with highly variable cross-sections, complex geometries, and construction sequences. The construction method was appropriate for two ventilation tunnels and two escalator shafts at Farringdon Station.
The tanked and double-bonded spray-applied membrane offered by TamSeal 800 prevented the risk of water traveling down the shaft along the membrane and filling up the space behind the sheet membranes installed in the platform tunnels.
The use of fully bonded TamSeal 800 waterproof membrane solution also prevented a reservoir build-up in the lower tunnels, avoiding the risk of constant water ingress issues if the sheet membranes in the lower tunnels would breach.
The bond strength for the connection between the spray and sheet membrane systems had to be tested to demonstrate the suitability of the material and the robustness of the connection details.
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Technical tests were conducted at the Normet test facilities in Coventry to assess the bond strength of TamSeal 800 onto concrete, sheet membrane and connection tape and the hardness development.
TamSeal 800 was applied in two separate 2 mm thick coats. The first coat was in orange and the second coat white. The contrasting coat colours application was used to achieve the correct thickness of 4 mm throughout, ensuring 100% coverage.
The geometry and slopes of the escalator and vent shafts meant that hand spraying from lifting baskets using an electric Normet Piccola pump set-up was the best way to meet performance specifications.
Any occurring water leaks were treated with TamPur 150 to allow successful membrane application and curing in preparation for the TamSeal 800.
Spray membrane technology and application method is a recent development in the UK tunnelling market. It was important to provide training and share information for applicators, engineers and client and consultant inspection teams.
Farringdon Station is a good example of how a combination of spray-applied and sheet membrane enhances the strong properties of both systems.
TamSeal 800 proved to be flexible for complex tunnel geometry and ease in forming the watertight connection to the previous sections by just over-spraying a 30 cm wide strip. Simple repair methods can be applied if the membrane is damaged during construction.
The long-term advantage of the sprayed membrane solution is the double-bond between primary and secondary concrete linings, preventing the development of water paths between the surface and the lower tunnels.
The success of TamPur 125 in stopping water ingress has opened doors for other Normet injection products. The Gold Line is highly interested in TamPur 150 for segmental crack repairs. Trials have been completed through Tempo, Normet’s recommended applicator both in the UK and in Doha. They are expecting to secure the crack repairing work of 7 km running track.
After hearing positive feedback from the Gold Line project, the Red Line North ordered TamPur 100 for a leak on its project. The performance of the product has been excellent, and the customer is happy with the results. Our polyurethane range yields effective results and the customers are our best recommendation.