IIRC, China mainly uses coal, and they are building 100 new nuclear power plants in the next 10 years.

BTW 400kmh is a an utterly insane fantasy, from every point of view.
The energy intensiveness of such travel cannot and SHOULD NOT be borne by the world, regardless of the pointy-nosed rushing into deep tunnels fantasies of train fans.

Governments and companies don’t generally take care of arguments like “SHOULD NOT”. IMO, China will be the first to push that limit because they have long distances to convert such high speed to real travel time savings, hydropower to feed the trains and premium pricing of HS trains to pay the bills for energy.

However, practically nobody likes ballasted bridges/viaducts/tunnels/trenches any more, and I have to agree with them; the ecological benefit is close to nil given required concrete structure, and the maintenance is a lot higher.

Once again incorrect. Modern trend is to stick with the technology that surrounds bridges and other structures. Ballastless sections in the middle of ballasted ones are maintenance nightmares and limit safe cant deficiency.

BTW ballasted track is actually the technology for steel bridges these days because weight and elasticity damp noise and vibrations very well.

The THSR line is all slab.

… common TBMs on the market …

There is no such thing.

BTW 400kmh is a an utterly insane fantasy, from every point of view.
The energy intensiveness of such travel cannot and SHOULD NOT be borne by the world, regardless of the pointy-nosed rushing into deep tunnels fantasies of train fans.

In the medium to long term I doubt that > circa 320kmh commercial speed will be sustained. Technically feasible isn’t the same as desirable, after all. Where are my moon shuttle, personal helicopter and jet pack anyway?

But of course from the contractor’s point of view, self-specifying and then being obliged to design and build to an out of this world 400kmh “requirement” has the immense advantage of increasing construction costs significantly. Just like their over-the-top stations, where maximizing construction budget and actively inhibiting efficient operations are the rules of their game. It’s not as if they care about operating an efficient modern rail network anyway — somebody else (one guess, hardy California taxpayers!) will be left holding that bag, as usual.

“‘Once the rockets are up, who cares where they come down? That’s not my department’, says Wernher von Braun.”