HS2 - A vanity project?

[Haydn1971]

Size/quantity of the tunnel wall segments would increase as well - so an increase in the amount of concrete required to construct them, plus all associated costs.

I'm sure if you are getting at this, but the larger the diameter tunnel, the greater the load is on the roof and wall segments, this will scale increasingly as the diameter increases.

 

[dviner]

I'm sure if you are getting at this, but the larger the diameter tunnel, the greater the load is on the roof and wall segments, this will scale increasingly as the diameter increases.

Actually, I was more thinking about the increase in circumference that results from the increase in diameter - hence the arc of the segments would need to be greater, or more segments required.

Of course, if the segments are thicker, then you're not getting as much increased diameter as first expected...

 

[HSTEd]

Tunnel wall segments- if you use them (shotcreting is coming a long way surprisingly fast) are a minor cost. After all they are just blocks of concrete cast on a production line.

 

[AM9]

Cross section of 10m diameter tunnel = 80 m sq approx
x 2 tunnels = 160 m sq total

Cross section of single 20m diameter tunnel = 314 m sq approx

Therefore you need to remove almost double the amount of spoil during construction for the same length of tunnel.

The amount of spoil to be removed is related to the square of the required usable diameter plus the additional lining thickness. So assuming a circular tunnel and that the construction of the lining requires a linear increase in thickness, a 20m tunnel requires four times the spoil mass/volume compared to a 10m one. There would also be four times the mass/volume of concrete liner for the larger tunnel.

 

[HSTEd]

In tunnel construction mobilisation costs and surveying are rather large fractions of the cost however - which are approximately the same for all reasonable sizes of tunnel

 

[Class 170101]

HS2 and HS3 will be needed to stop us running out airport capacity sooner than we otherwise will.

Runway capacity freed up from Domestic flights can be used for International flights. Runways are far more controversial than railways.

I would also suggest that some airports would be more attractive for International carriers if they had better inward and outward land based connections. Why fly to London for Leeds and Newcastle if connections to Manchester are just as good.

 

[fowler9]

We don't need more runway capacity. You can stick loads more bigger planes in Manchester already. Virgin have recently replaced A340-600's with smaller aircraft. That said Thomas Cook are increasing their Trans Atlantic flights from Manchester.
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Oh yeah, Singapore are stopping their call at Munich which is annoying.