SMALL DIAMETER TBM/PIPEJACKING | TRENCHLESS
Above left, figure 17: 50T Crane – horizontal line load Above right, figure 18: 42T excavator – horizontal line load
frame was removed. This is an example of the effective collaboration between all parties to resolve challenges encountered during the works. During a site visit to view construction progress, a steel fixer provided constructive feedback with regards to detailing radial bars around the pipe openings. The insight into challenges of working with long sections of radial bars as opposed to overlapping straight bars will contribute to solidifying the relationship between designers and contractors. Figure 12 shows the reinforcement and temporary
works for the back wall of the thrust pit. This reinforcement was checked against the jacking loads provided by Active Tunnelling. The jacking loads from the TBMs resulted in a hogging moment generated within the base slab of the pit. Larger reinforcement bars in the top face of the slab (B20’s) were installed to resist this moment. Similarly for the back wall of the thrust pit B20’s were used in the front face. The reinforcement was a demonstration of integration between temporary works and permanent works. A shear key was introduced into the temporary
design by Active tunnelling to increase the passive resistance from the soil during jacking operations. The shear key was connected to the base slab with reinforcement designed by the temporary works
designer but also transferred loads into the permanent slab beyond the shear key. Figure 11 below shows the different interfaces between permanent and temporary works. The temporary sheet piles shown in magenta formed the cofferdams which were used to assist with groundwater. The piles minimised working time required with machines at the site adjacent to the railway line. A temporary base slab was also constructed which would eventually be burnt off. Figure 13 shows the three TBMs installed within the
thrust pit. These machines embedded themselves into the embankment, outside of the track support zone in readiness for the possession being granted. Figure 14 shows the jacking plates required on the back wall to spread the load from the machines. The jacking loads were checked against the permanent design in the form of both hand calculations and analysis software. Figure 15 shows a view from the thrust pit looking towards the reception pit on the other side of the railway. The sheet piles adjacent the railway embankment will remain in place with the other sections being withdrawn once the concrete sections reach the specified design strength. Figure 16 shows the 50 tonne crane and two 42 tonne
excavators adjacent to the thrust pit. These machines were key to the successful construction of both pits,
Above, figure 19: Midas FEA model of thrust pit with all ULS load cases September 2024 | 17
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53
