[HN Gopher] The Evolution of Tunnel Boring Machines (2023)
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The Evolution of Tunnel Boring Machines (2023)
Author : chautumn
Score : 77 points
Date : 2025-01-05 10:58 UTC (12 hours ago)
(HTM) web link (www.construction-physics.com)
(TXT) w3m dump (www.construction-physics.com)
| dkga wrote:
| Nice text! I'm just surprised at the lack of mention of the
| techniques used in the Gotthard in the 19th century.
| bluGill wrote:
| Despite TBMs being used all the time it is genererally much
| cheaper to build a tunnel by cut and cover - that is just call in
| excovators and dig a hole then cover it. when an excavator breaks
| you push it aside and get another until it is fixed. Want to go
| faster - just hire more excavators the overall cost is the same
| since you are done faster.
|
| tbms are cheaper if you must go deep, but deep is a negative for
| subways since people must get down which takes time (faster is
| always better).
|
| It is claimed that cut and cover is toa much surface disruption -
| but cut and cover is much faster and so the disruption to any one
| place can be quick enough. Better to manage disruption than
| eliminate it.
|
| when a tbm breaks your project is delayed while you wait for
| parts and then fix it in place.
|
| Tbms do go under everything else, but experience proves you can
| find things and go around them quick enough (sometimes there is a
| delay as somethingeof archeological interest is found - but
| evperience shows this is still cheaper than a TBM.
|
| Yes TBMs are cool and useful but the simple shoud not be over
| looked
| rsynnott wrote:
| Thing is, you're often building these under already-existing
| things. The Dublin metro project is facing significant planning
| challenges on the basis that thousands of homes and businesses
| passed can complain about speculative vibrations from the TBM;
| with cut and cover it would just be a complete nonstarter (I
| think one small section is planned to be cut and cover, but
| most of it will be either bored or surface rail).
| bluGill wrote:
| That is a poor excuse - places with much worse problems have
| don cut and cover.
| aaron695 wrote:
| > it is genererally much cheaper to build a tunnel by cut and
| cover
|
| Coolo, you are building tunnels in a city that doesn't exist
| yet.
|
| Start here - https://en.wikipedia.org/wiki/Opportunity_cost
|
| Do you have any interesting examples of modern day cut and
| cover that are not part of a TBM run?
|
| > TBMs are cool and useful
|
| They are what is needed to move humanity forward.
|
| You have trillion $ centers that using 3D you can add massive
| amounts of access to. This is not like reclaiming land from
| water, which is ~stealing, this is value adding through
| topography, it's creation.
| lukan wrote:
| I vouched for this comment, but you might want to check your
| general style of communication and then email dang about your
| apparent shadow ban.
| bluGill wrote:
| The tunnel will be around for 100 years. Not much ophortunity
| cost is lost. And you lose the ophortunity cost of what ever
| you would spend the saved money on for ever. A longer line
| for example.
| tobylane wrote:
| You're often not just building under existing things, but
| through them. We now have a lot under the roads. The Victorians
| built the subsurface lines of the London Underground with cut
| and cover, but Oxford is currently suffering overrunning works
| to lower a road under the station, because of unknown brick
| arches and utilities. Even the TBMs are building beside
| existing tunnels and basements.
|
| What projects in developed countries have used cut and cover
| recently? In trying to find out, I see that HS2 under west
| London and the Canada line under Vancouver chose tunnels over
| cut and cover because it was cheaper.
| lytfyre wrote:
| > I see that [...] Canada line under Vancouver chose tunnels
| over cut and cover because it was cheaper.
|
| Canada Line was mostly Cut-and-Cover - only the bits below
| downtown and crossing below the water were bored, the bulk of
| the underground was done cut and cover for cost and speed to
| make sure it opened for the 2010 olympics.
|
| It was not a popular choice - not really announced before the
| project was approved, and local businesses along the route
| took a big hit.
|
| Vancouver's current Broadway Line Extension is being done
| with TBMs to avoid the impact that the cut and cover canada
| line segment construction had.
| mitthrowaway2 wrote:
| It also resulted in a rail line that has to slow down
| significantly to round screeching curves along the path of
| the road above.
| peterpost2 wrote:
| > What projects in developed countries have used cut and
| cover recently?
|
| I know in Sweden the Vastlanken project partially used cut-
| and-cover at least for the part going southwards..
|
| https://en.wikipedia.org/wiki/West_Link
| bluGill wrote:
| The article said out of 89 current projects 80 were TBM so it
| isn't surprising you don't know of the exceptions. I don't
| off the top of my head either.
| rob74 wrote:
| I imagine it's also a bit difficult to separate it this
| cleanly, as most bigger projects will probably use a mix of
| technologies: cut and cover where possible (if it leads to
| savings), TBMs or other technologies like NATM (https://en.
| wikipedia.org/wiki/New_Austrian_tunneling_method) for the
| rest. Even if TBMs are used for the tunnels, cut and cover
| will probably be used for things like stations, emergency
| access points and intermediate TBM starting points (of
| course, the TBM starting points might be future stations).
| grvbck wrote:
| > What projects in developed countries have used cut and
| cover recently?
|
| Not really a new project, but parts of the subway in
| Stockholm are cut and cover. One of those tunnels (from the
| 1930s) has been leaking in water for some years and is up for
| a total overhaul, so basically digging up everyting and doing
| a new cover.
|
| The section is 8 m wide and 925 m long, projected timeline is
| 6-7 years starting this fall. It will be a massive project,
| as one of the busiest streets in Stockholm is directly on top
| of it.
| Haemm0r wrote:
| More information on cut and cover:
| https://de.m.wikipedia.org/wiki/Neue_%C3%96sterreichische_Tu...
|
| (better translate from the german version, as it has more
| information and examples)
| abduhl wrote:
| This is not cut and cover. Cut and cover is when you "cut" an
| excavation from the ground surface down and then "cover" it
| back up with dirt after constructing the structure you want
| below ground. You have linked to an article on NATM, which is
| a conventional (read: non-TBM) tunneling method.
| bluGill wrote:
| Cut and cover often is cover than dig - there are a lot of
| options
| abduhl wrote:
| Cut and cover is what I described: excavate down, build
| the structure, cover it up. I am aware that there are
| lots of options, you can browse my comment history and
| see that I probably have more experience designing and
| constructing underground infrastructure (and tunnels in
| particular) than anyone else that posts on HN.
| Haemm0r wrote:
| I see; you are competely right, I am not really familiar
| with the the technical terms and messed up with just
| literally translating "cut and cover".
| jeltz wrote:
| Cut and cover only works if your subway follows streets. Yeah,
| I think we should do that where it makes sense but quite often
| you need to go under buildings or hills.
| potato3732842 wrote:
| TBMs are for going around problems. Compared to cut and cover
| you can ignore entire classes of people who would be,
| expensive, delaying obnoxious stakeholders.
|
| <gestures at the contents of an average HN comment section
| whenever the subject is public infrastructure>
| yongjik wrote:
| My neighborhood in Seoul got a new subway line while I grew up,
| I believe they used cut-and-cover (it was almost at the
| outskirt, so they didn't have anything else underground) and it
| took several years.
|
| So, while it's doable, it's not exactly "Just dig a hole, build
| the tunnel and cover, done." It's a major disruption to shops
| along the street.
| bluGill wrote:
| It is a major disruption for a couple years.
| larsga wrote:
| It's not a choice of TBM vs cut-and-cover. You also have drill-
| and-blast. Which method is better depends on a number of
| factors, including depth and the state of the soil/rock you're
| going through.
|
| A problem with TBMs is it can be difficult/costly to secure the
| tunnel sufficiently against water ingress. If you mess up that
| one the cost of your tunnel can easily double or more.
|
| Here in Norway we recently built a railway tunnel with TBMs
| (Blixtunnelen) and it's having problems with water ingress. A
| fairly mild problem relative to how bad these can get, but it's
| enough that the tunnel constantly has to be closed for repairs
| to the railway infrastructure due to water drips.
| rsynnott wrote:
| So it doesn't seem to be mentioned here, but has there been some
| major recent change in the economics of the _scale_ of the
| tunnels? Dublin's beleaguered metro project recently put out its
| new design; there are a bunch of changes from the previous early-
| noughties design, but one of the more eyebrow-raising ones is
| that the bored sections will now be a single _9.5 meter diameter_
| tunnel; it is claimed that this is less disruptive and cheaper
| than the two-narrow-tunnel approach used in conventional bored
| metros. Recent metro lines is Barcelona and Madrid have also used
| the single-giant-tunnel approach.
|
| Anyone know what's going on here? Intuitively you'd expect two
| small tunnels to be cheaper; you're moving a lot less material.
| timschmidt wrote:
| I suspect the cost is not in volume of material removed, but in
| operation and maintenance of the machine and it's crew. One
| tunnel instead of two is half as much machine and crew time.
| freeopinion wrote:
| Please explain how you reasoned this out. If one 9.5m tunnel
| requires 70 m3 of removal for every meter of forward
| progress, and two 5m tunnels requires 40 m3 of removal for
| every meter of forward progress, won't it take nearly twice
| as long to dig the single larger tunnel? Won't that require
| twice the machine hours and twice the crew hours?
|
| How does the volume of material removed not directly impact
| machine and crew costs?
| jcgrillo wrote:
| Two dump trucks can't pass eachother in a 5m tunnel.
| That'll put a restrictive upper bound on material removal
| rate which isn't present in the larger tunnel.
| timschmidt wrote:
| Seems like larger machines are likely to have larger
| material removal rates. Dependent on the surface of the
| digging tool and it's feed rate.
| Hilift wrote:
| One of the references in the article mentions using
| better alloys ("modified tool steel") and 20" discs
| produces better results and lower overall costs due to
| time between disc replacement. This could be A8 "chipper
| knife" steel.
|
| https://www.robbinstbm.com/wp-
| content/uploads/2017/07/Smadin...
|
| https://www.litechtools.com/products/tbm-disc-cutter/
| timschmidt wrote:
| Makes sense. I was thinking more about the face of the
| machine itself being larger, likely the size of the
| tunnel, and would contain many such 20" discs. In other
| words, given that the material removal rate of each disc
| is likely fairly similar from machine to machine, the
| machine with more of them removes more material at once.
| metalman wrote:
| Two of everything, ventilation, electrical, water, telecoms,you
| name a system, and then name it again. Chances are that set
| backs required for engineering and existing infrastructure will
| be challenging, with two parallel sytems. edit: there is an
| assumption that the space required undergroud is free and
| infinite, when in fact two tunnels with set backs and spacing
| will require more total space than one larger tunnel and will
| then limit the availible area for deep building foundations and
| anything else. Then we get to interchandes, and emergency
| access. And there is a ready market for any material removed
| from the dig, which will be a very routine operation. And while
| the volume of fill removed will be greater, the internal volume
| per cubic foot of tunnel wall will also be greater, allowing
| for more generous alotment of space for future systems and
| untilities, bigger wider lanes, etc. Somewhere I came across a
| journal, just for tunnel makers, and there equipment. And
| recent reports have tunnels bieng completed ahead of schedule
| and on budget, so they are infact, taking care of business.
| rsynnott wrote:
| Oh, yep, I've no doubt that if they can ever actually get
| planning through for the damn thing, they'll be able to build
| it. In Ireland it's generally the planning that's the
| problem.
|
| What I'm curious about, though, is what, if anything, changed
| to make this single-bore approach suddenly popular. A lot of
| new metro lines seem to be built that way, but old (and not,
| like, 19th century, even most 20th century stuff) always seem
| to be double-bore.
| baumschubser wrote:
| I want to mention a recent extension to Berlin's subway system
| right in the middle of the city, in swampy ground and below a
| canal. They injected ,,freeze lances" into the ground, turned
| 43,000 m^3 of mud into an ice block and then carved their way
| through it. Absolutely amazing engineering, I think planned and
| executed by a Swiss company.
| Haemm0r wrote:
| Got a link for this? I am interested :-)
| pwarner wrote:
| Big Dig also used ground freezing.
| https://babelniche.com/2024/01/17/innovations-of-the-big-dig...
|
| And the Erie Canal dig the sections through swampy ground in
| the winter. That was partially to avoid Malaria. Circa 1825
| padenot wrote:
| This is also a technique that was used more than 100 years ago
| for the line 4 of the Paris metro:
| https://www.ratp.fr/en/discover/out-and-about/culture/histor...
| llsf wrote:
| Funny that they had to freeze the ground to dig it, as it is
| one of the hottest line in Paris (at least 20 years ago).
| s1artibartfast wrote:
| My understanding is that the freezing is normally about
| stopping water intrusion long enough to drill and place
| concrete
| ReptileMan wrote:
| How is The Boring Company doing lately? There will be huge
| induced demand for tunnels if they manage to deliver even close
| to their goals.
| grecy wrote:
| Slow and steady progress. They're just about to go big in
| Vegas, with tunnels the length of the strip.
| youngtaff wrote:
| The strip is 4 miles long... when Musk company can bore
| longer, wider tunnels avoiding other infrastructure e.g.
| London tube lines, sewers etc then they might have something
| to shout about
| jeltz wrote:
| Is there any reason to think they will be able to? They are
| just going the same thing as everyone else but started later.
| Another player might lower costs slightly but not much.
| ReptileMan wrote:
| No reason, but Elon style is - if he delivers to deliver
| qualitive and not quantitative improvements to technology.
| youngtaff wrote:
| They're also boring much smaller tunnels which have much
| smaller costs
| ChrisArchitect wrote:
| (2023)
|
| Some more discussion then:
| https://news.ycombinator.com/item?id=37836889
| kitd wrote:
| Interesting article. This bit was not what I was expecting:
|
| _Today, rock tunneling machines have achieved tunneling rates of
| over 700 meters per week, and soil tunneling machines have
| achieved rates of over 200 meters per week, though this is
| dependent on the size of the TBM_
|
| Ie, that rock tunneling can be > 3x quicker than soil tunneling.
| ewhanley wrote:
| Rock often has sufficient structural integrity to get by with
| some bolting vs adding structure (steel, shotcrete, etc) to the
| soil tunnel as they go
| Gibbon1 wrote:
| It never seems to get stated directly by tunneling through
| stable rock has to be really easy. Like if you can drill and
| blast your way through you just need a small crew of workers
| and a dump truck.
|
| There is a half mile long tunnel in the California desert
| that an addled miner made with hand tools and dynamite over
| 38 years. Self funded and part time.
|
| https://en.wikipedia.org/wiki/Burro_Schmidt_Tunnel
|
| Then digging through unstable rock with water intrusion and
| danger of flooding the costs have to go way way up.
| bilsbie wrote:
| I wonder how far off we are from vaporizing the material and
| venting it out of the tunnel.
|
| Probably way more expensive but you could go faster and don't
| need to deal with hauling the material out. It might glassify the
| surrounding soil and make its own support structure too.
| gosub100 wrote:
| This topic has been mentioned in regards to digging super deep
| bore holes for geothermal energy. The high temps a couple miles
| down started to soften metal drill bits but some companies are
| working on lasers that are capable of melting rock to allow
| further digging.
| lightedman wrote:
| An 80W CO2 LASER is plenty of power. I regularly engrave the
| living shit out of stone with mine, and that goes a few
| millimeters deep.
|
| Get a couple kW in the same wavelength (10640nm) with a
| proper adjustable focus (movable diopter) and a galvo and a
| vacuum assist and you can just start raster-scanning your way
| through the rock.
| bilsbie wrote:
| Has anyone studied how roots tunnel underground so effectively?
| Maybe we can copy aspects of that.
| staplung wrote:
| Yes, they have been. The growing tip of a root is called the
| root apical meristem[1] but the short story is that they work
| effectively by being tiny and taking years or decades to
| develop, so not all that helpful in terms of making things
| easier or cheaper. They also can't really go through rock,
| though they can often split them, particularly if they have
| fractures already.
|
| [1]:
| https://en.wikipedia.org/wiki/Meristem#Root_apical_meristem
| yongjik wrote:
| While we're talking about cool boring technologies... I once
| heard that Seoul's Bus Terminal Station, line 9, was a
| particularly difficult case. Line 9 had to go beneath existing
| line 3, but it couldn't go too deep because it (obviously) needed
| to connect to the rest of the line.
|
| In the end they thrust a group of horizontal steel pipes to
| stabilize the soil and dug beneath it - and those pipes were 15
| cm(!) below existing line 3.
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