3 ms·

> 1) the boring machine isn't the biggest cost, so if TBM speed were an important factor and you want faster digging now you can use multiple TBMs Yes but redu

> 1) the boring machine isn't the biggest cost, so if TBM speed were an important factor and you want faster digging now you can use multiple TBMs Yes but reducing the cost of something that "isn't the biggest cost" which directly effects the things that are the biggest cost does seem to be beneficial. > 2) the current labor costs in the US is primarily a "political rather than technological problem" Which is why a boring machine which reduces overall labor costs through increased efficiency and automation also seems to be beneficial. > 3) bore size doesn't have that much of an effect on overall cost "The Barcelona Line 9 doesn’t use the 12m diameter stacked tunnel along its whole route. Some sections are built using different construction methods, presumably because they are cheaper. This mostly depends on the local geography and available space."[0] "This is why there’s a trend toward bigger tunnels, as a cost saving mechanism: BART’s San Jose extension is studying different tunnel approaches, one with a large-diameter tunnel and one with twin small-diameter tunnels, and the cost turns out to be similar. " One could be excused to think 1 large tunnel == 2 small tunnels would imply that one small tunnel would cost about half of one large tunnel. As an aside, I grew up out there, why they even digging tunnels, not like there's a mountain between Fremont and SJ? Still not seeing a reason why it isn't possible to make digging tunnels efficient enough to...actually, why are we even arguing over how some rich dude choses to spend his money? [0]http://www.cat-bus.com/2017/10/barcelonas-line-9-inspiring-montreals-pink-line/ http://www.cat-bus.com/2017/10/barcelonas-line-9-inspiring-m...

eesmith 9y ago
Regarding 1), certainly it reduces other costs. But the article points out that each additional TBM drive, including those extra costs, adds only about 10% to the overall cost of the tunnel. "The rest is dominated by labor and materials that are insensitive to tunnel width, such as interior lighting and cables." It then points out that "the actual cost is even less sensitive to tunnel width. The VLHC study only looks at the cost of tunneling itself. In addition, there must be substantial engineering. This is especially true in the places where transportation tunnels are most likely to arise: mountain crossings (for intercity rail), and urban areas (for urban rail and road tunnels)." While on the other hand, the smaller tunnels means more complex junctions, including "forcing underground four-level interchanges". This helps explain why one small tunnel might cost more than 1/2 the price of a large one. 2) "increased efficiency and automation" are technological solutions. One of the costs is union featherbedding, which is a political problem not easily solved by such a technology solution. 3) "The Barcelona Line 9 doesn’t use the 12m diameter stacked tunnel along its whole route". The same reference also says "The metro line is almost completely contained in this single tunnel". Certainly if you can get away with cut-and-cover then there's no need for an expensive TBM. Regarding "why they even digging tunnels, not like there's a mountain between Fremont and SJ", I don't know about that project but I know that in other projects the main options are either surface or elevated trains. Surface means at-level crossings, which are dangerous and stop road traffic. Elevated is safer, though more expensive. Both require condemning expensive land, and people will object to the sound and visual impact, and file lawsuits. Also, underground routes can usually go straighter. You asked "actually, why are we even arguing over how some rich dude choses to spend his money?" We do this all the time. People complain when the Koch brothers use their billions to help push politics in a direction they favor. People complain when Bill Gates uses his billions to help push education policy in a direction he favors. In both cases one of the objections is that money amplifies influence, to the point where one rich person's whims can have more political influence than the serious concerns of tens of thousands of other citizens. Including experts. It's also a problem should public institutions start to fund projects which are fundamentally flawed. And finally, I'll argue that your question is misdirected. The article is not about "how some rich dude choses to spend his money" but rather an argument directed to people who have already decided to listen to a rich dude, in order to dissuade them of their enthusiasm.

eesmith 9y ago

Regarding 1), certainly it reduces other costs. But the article points out that each additional TBM drive, including those extra costs, adds only about 10% to the overall cost of the tunnel. "The rest is dominated by labor and materials that are insensitive to tunnel width, such as interior lighting and cables." It then points out that "the actual cost is even less sensitive to tunnel width. The VLHC study only looks at the cost of tunneling itself. In addition, there must be substantial engineering. This is especially true in the places where transportation tunnels are most likely to arise: mountain crossings (for intercity rail), and urban areas (for urban rail and road tunnels)." While on the other hand, the smaller tunnels means more complex junctions, including "forcing underground four-level interchanges". This helps explain why one small tunnel might cost more than 1/2 the price of a large one. 2) "increased efficiency and automation" are technological solutions. One of the costs is union featherbedding, which is a political problem not easily solved by such a technology solution. 3) "The Barcelona Line 9 doesn’t use the 12m diameter stacked tunnel along its whole route". The same reference also says "The metro line is almost completely contained in this single tunnel". Certainly if you can get away with cut-and-cover then there's no need for an expensive TBM. Regarding "why they even digging tunnels, not like there's a mountain between Fremont and SJ", I don't know about that project but I know that in other projects the main options are either surface or elevated trains. Surface means at-level crossings, which are dangerous and stop road traffic. Elevated is safer, though more expensive. Both require condemning expensive land, and people will object to the sound and visual impact, and file lawsuits. Also, underground routes can usually go straighter. You asked "actually, why are we even arguing over how some rich dude choses to spend his money?" We do this all the time. People complain when the Koch brothers use their billions to help push politics in a direction they favor. People complain when Bill Gates uses his billions to help push education policy in a direction he favors. In both cases one of the objections is that money amplifies influence, to the point where one rich person's whims can have more political influence than the serious concerns of tens of thousands of other citizens. Including experts. It's also a problem should public institutions start to fund projects which are fundamentally flawed. And finally, I'll argue that your question is misdirected. The article is not about "how some rich dude choses to spend his money" but rather an argument directed to people who have already decided to listen to a rich dude, in order to dissuade them of their enthusiasm.