I was discussing HS2 with my sister's hubby the other week concerning the cost of the project. He is a retired materials manager for Balfour-Beatty and has been foundation design authority responsible for many road and rail projects both here and abroad. He explained to me that one of the major costs of any major transport infrastructure project is the soil structure beneath the ground surface.
It's all way over my head/under my feet, but it's something like this: For a 100 mph railway the soil must be stabilised to a minimum depth of 4 metres; for a 200 mph railway the pressure front is active a lot lower, so they would need to stabilise the soil to a typical depth of 20+ metres.
That is a huge cost to be undertaken before any of the sub-base or formation is even begun.
Failure to stabilise results in localized soil liquefaction, (like wot happens with earthquakes, or dabbling your toes on damp sand), causing failure of the formation, mis-alignment of track, etc with subsequent costly delays and repairs.
There was a whole raft of other stuff he told me about, but he is a road/rail soil engineer, I am an electronics engineer, and my brain got clogged in a short space of time.
As for high-speed bridge foundations, that is another kettle of fish!
My idea of foundations is dig hole, pour concrete, build whatever on top, and be glad we don't have earthquakes here.
(My house was built on a flood-plane 115 years ago; the old maps say 'liable to flooding, not suitable for building'. The railway at the bottom of the garden has wobbled the the whole lot into the ground with every passing train; My wshop stands on a 7.25 cubic metres slab that wobbles when a lorry goes past on the bypass 200 M away.
Sorry about the ramble, got carried away.
