quantinghome
Established Member
- Joined
- 1 Jun 2013
- Messages
- 2,265
Haven't they decided that yet? How do you replace slab track and high speed points in the space of 5 hours? Does anyone know how long slab track lasts with 18 tph at 400kph? Possibly not, as no-one has tried it. The M42 and the M1 are still settling on the bits constucted over old mineworkings etc. Presumably the cost of HS2 includes everything necessary to ensure that it will not settle at all.
Slab track has been around for some time so I would guess maintenance and renewal issues are well-understood. According to a quick google, slab track life span is around 60 years, so renewal would be pretty infrequent compared to the operations required to renew ballasted track. I disagree that 'no one knows how long slab track lasts with 18 tph at 400kph'. The long term behaviour of reinforced concrete is well-understood science both in terms of chemical and dynamic fatigue effects. The design could be adequately assessed for life span using structural design codes. I would imagine that HS2 are supplementing this with extensive case studies of existing high speed slab track and possibly laboratory testing of the proprietary slab systems available.
You are right that the settlement tolerances for HS2 will be significant tighter than for motorways (although you can never get zero settlement). Again, this is a well understood phenomenon for which engineering solutions are readily available. For example, HS1 crosses the Rainham marshes on a piled track bed, effectively a viaduct at ground level. HS2 are looking to minimise ground movement in line with their aim to design out as much maintenance requirement as possible.
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