SHAFTS, CAVERNS - BTS HARDING PRIZE COMPETITION | TECHNICAL


4. LESSONS LEARNT FOR THE NEXT SLIPFORM Although the slipform operation was an overall success, several improvements could be implemented to enhance efficiency and outcomes in future projects. Greater preparatory work at the outset would have reduced stoppages during rig adaptations. Specifically, constructing the hanging deck at ground level would allow easier modifications, minimise work at height, and accelerate the process. Boxouts at the top of the shaft should have been


struck from the hanging deck while the rig was installed, rather than using a Mobile Elevating Work Platform (MEWP), which would have improved safety and productivity. Finally, the widened section of the rig, which proved vulnerable to deflections, could have been designed with additional support to stiffen the structure and maintain its shape throughout the slipform operation.


5. CONCLUSION The slipform secondary lining works represented an exciting and rewarding project, from the initial site preparations through to the pouring of the final wagon of concrete. Extensive preparation prior to commencement ensured that the slipform process ran smoothly, resulting in a high-quality finish. This allowed the teams to dedicate more time to collaborative problem solving and ultimately delivered a watertight lining, ready to serve its operational purpose of diverting sewage flows from the River Thames, Figure 16. By the end of 2025, the tunnel has successfully


diverted and captured approximately 12 500 000 tonnes of sewage that would otherwise have entered the river. This volume is equivalent to around 5000 Olympic-sized swimming pools. Although no storm event has yet been large enough to fill the CARRR shaft, it is anticipated that the shaft will reach capacity up to five times per year.


April 2026 | 27


6. ACKNOWLEDGEMENTS I would like to extend my thanks to every member of the BMB JV team, and in particular to my shift team, whose commitment and cooperation made the site both an enjoyable and safe place to work. I am also grateful to the Client, Thames Tideway, and to the designers, MSES and Hewson Consulting, for their support and expertise. The success of major construction projects relies


on strong collaboration, and this was the primary factor behind the successful delivery of the slipform. I would further like to acknowledge all those who have supported me throughout my career and provided opportunities to contribute to challenging and rewarding projects.


Left:


The complete shaft secondary lining


Above:


A scan of the complete concrete secondary lining. Green is the design thickness; dark red are 50mm thicker than design, dark blue are 50mm thinner


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