HARDING PRIZE COMPETITION 2024 | BTS
team, I developed a detailed but flexible procedure defining responsibilities of the team members and the lines of communication to review and enact changes. This was effective and gradually adjusted to suit the needs of the project at its different stages. Throughout the TW adit construction, I provided the
link between site and back office teams and actively participated in the daily review meetings (DRMs) as the Jacobs design manager. With participation from multiple parties and being led by an independent organisation, BeMo Tunnelling, the meetings enable group consensus to be reached following review of monitoring and geotechnical data to identify possible movement trends and any requirement for toolbox measures. To ensure works are undertaken in a safe and effective manner in line with the design requirements, the DRMs thoroughly review completed and planned works ahead of the next phases of activity. To control work in the field, the DRMs develop agreed Required Excavation Support Sheets (RESS) documents from the design.
Probing & grouting At each TSC location, the original ground investigation consisted of a single shaft borehole. To verify the ground conditions and associated design, a further
investigation was undertaken using core holes, prior to mining breakout from the segmental main tunnels and commencement of main TSC construction work (see Figure 3). Following breakout from the segmental tunnels and
prior to each significant advance of the SCL adits, further forward probing holes were installed to inform the contractor of the likely ground conditions ahead. To allow the ground conditions to be better
understood, throughout the construction of the TSC, the geotechnical information obtained from probing and mapping the tunnel face is logged within a 3D geological model to allow it to be scrutinised and called upon as required in future. To reduce the severity of likely water ingress to
permissible levels during the construction of the TW, a significant campaign of probing and grouting gets undertaken prior to breakout from the segmental tunnels. The extent of grouting required varies by location depending on the ground conditions encountered, and due to the need to balance time and cost against likely reductions in flow without fracturing the ground. Grouting was undertaken using microfine grouts due to the specific hydrogeology of a location. See Figure 4 for an example of a geological feature being grouted.
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Above, figure 2:
TSC geometrical overview PHOTO CREDIT: BALFOUR BEATTY
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