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UK
HS2
Balfour Beaty Vinci Joint Venture (BBV)
The HS2 Long Itchington Wood Tunnel North Portal project required a complex and comprehensive approach to temporary works for the successful launch of two large-diameter Variable Density TBMs. OTB Engineering was responsible for designing and implementing a suite of temporary works that included thrust frames, launch rings, seal cans, TBM gantry cradles, and PCC ring support frames. Each element was meticulously engineered to ensure the safe and efficient launch of the TBMs from the prepared site.
A critical aspect of the project involved the design and installation of the seal can structure, which had to fit tightly against the sprayed concrete lining (SCL) surface. This structure needed to provide a high degree of watertightness, essential for the TBM’s operation during its initial excavation stages. To achieve this, OTB processed detailed point cloud data of the SCL face provided by the contractor, identifying areas of potential clash and enabling the contractor to remove the hight points from the SCL surface before positioning the seal can. This proactive approach significantly reduced gaps at the interface, minimising the grout volume and additional mitigation required.
Following the launch of the first TBM, OTB introduced several improvements to streamline the process for the second TBM launch. The design of the PCC ring support frames was simplified to reduce installation time and effort, and anti-roll plates were developed to replace the traditional anti-roll shoe system. These plates, bolted securely to the TBM, eliminated the need for sliding plates and hot works for removal, allowing the pre-installation of support frames for the PCC rings. Additionally, “sandboxes” were incorporated into the thrust frame supports, facilitating the controlled release of prestress during removal, enhancing efficiency and safety.
Through careful planning, innovative solutions, and a commitment to precision, OTB delivered a robust, reusable temporary works package that supported the successful launch of both TBMs. This project exemplified OTB’s expertise in tunnel engineering and its ability to solve complex challenges, contributing to the timely progress of the HS2 initiative.
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