TECHNICAL | SHAFTS, CAVERNS - BTS HARDING PRIZE COMPETITION
Right:
Slipform rig jacked in 50mm layers
The positions of the near and far face reinforcement were marked on pins installed into the primary lining, allowing accurate placement of the vertical bars despite variations in lining thickness. I carried out routine checks throughout the process and communicated directly with operatives whenever adjustments were necessary. By ensuring accuracy at the outset, the reinforcement was correctly aligned, which facilitated smooth progress during slipforming and eliminated positional issues with the steel.
Right: Couplers cast into the lining
2.7. Emergency procedures Due to the significant changes to the working area prior to commencement of the slipform operation, a series of emergency procedures were carried out. I marked out designated clear zones for the emergency manrider and conducted injured person trials to validate rescue arrangements. Following these trials, I recommended enlarging the access hatch to facilitate the safe and efficient recovery of an injured person from the hanging deck, thereby improving response times in the event of an incident. The complete rig is shown in Figure 4, which
highlights the location of the emergency stretcher zone on the left-hand side. In addition, I instructed the carpenters to construct shelving for the storage of MSA units. This ensured that all personnel were aware of the location of life saving equipment and reduced the risk of trip hazards caused by devices being left unsecured on the deck.
personnel having a clear understanding of upcoming requirements, particularly where cast-in items and rig modifications were involved. This forward planning created additional capacity to address inevitable issues during the slip, which is inherently a fast-paced operation with limited opportunity for downtime.
2.5. Installing the steel reinforcement Steel reinforcement pre-fixing was undertaken to reduce the workload on the steel fixers at the start of slipforming and to ensure the correct positioning of the starter bars. Using the TunnelBeamer, a tablet loaded with the finished shaft profile, I set out the bars to maintain the specified 75mm cover and the required 200mm bar spacing. This task demanded careful interpretation of the complex reinforcement drawings.
22 | April 2026
3. SLIPFORM OPERATION The slipform operation was delivered under a 7/4/7/3 shift pattern, with each shift lasting 12 hours. The gangs worked seven consecutive days, followed by four days off, then seven consecutive nights, followed by three days off. Three shifts were maintained daily, comprising a day shift, a night shift, and an off shift, with site hours running from 07:00 to 19:00. Handover at the face was critical to ensure continuity of the slipform process. Each gang consisted of six steel fixers, six carpenters, six concrete operatives, two concrete testers, one pump driver, three slingers, a foreman, and two engineers. On average, each shift poured approximately ten
wagons of concrete, equating to 75m3, which enabled the slipform rig to climb by roughly 1.5m per shift.
2.6. Survey control As the slipform rig advanced up the shaft, the control prisms located at the top would become obstructed. To mitigate this, I installed additional survey control points into the base slab prior to commencing slipforming. I also tested the instrument setup in several key locations that I anticipated would be required during the operation. By uploading all survey data onto the EDM and establishing the most effective setups in advance, I was able to share this information across shifts. This proactive approach reduced potential obstructions during the slipform process and ensured that concrete pouring could continue without interruption.
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