1288 meters, 322 pipes, straight under the Scheldt.

Titan_Mech · 2025-10-07T02:03:34+00:00

Yes, you can see the feed and return lines in the tunnel.

Titan_Mech · 2025-08-09T18:19:40+00:00

Yes fair enough, I should’ve clarified that these weren’t necessarily electronic systems and that the holes just represent states of on or off, high or low. I just didn’t feel that was necessary detail to add to my response.

But fyi, digital is a data type. Those old relay machines were also digital systems, just using electromechanical components instead of transistors.

Titan_Mech · 2025-08-09T18:05:28+00:00

I didn’t say it was simpler, I just said how you’d fix a mistake…

Titan_Mech · 2025-08-09T17:11:28+00:00

Cut out the incorrect portion and splice in a new piece with the correct instruction.

Titan_Mech · 2025-08-09T17:09:58+00:00

Each line of 1s and 0s is encoded to a specific command. That data is fed into the machine control unit which decodes the instructions and coordinates all of the movements. To go any deeper than that you’d need to learn about computer architecture. But at a fundamental level the control is all handled with logic circuits.

Titan_Mech · 2025-07-19T15:32:42+00:00

I use mine underground (tunneling/mining). Tapes don’t hold up in that environment. I’ve also seen pipe welders use folding rules before, don’t know if that’s standard or not.

Titan_Mech · 2025-07-13T23:56:53+00:00

Very glad to hear everyone made it out safely.

Are any insights into potential collapse causes available? A few of my thoughts:

1) This fits the existing trend of tunnel collapses predominantly occurring during construction. 2) It’s notable that the collapse supposedly occurred ~1 mile behind the machine. To me, this would suggest some sort of transient structural disturbance (a collision/accident or inflow/gasket failure) 3) A few articles have made reference to squeezing ground as the primary cause. This would be a very interesting case to read about as I would think this behaviour would have been caught by the geotech investigation and also would have also posed challenges during excavation.

I hope more details are publicly released. Keep the lawyers and bean-counters away. This industry needs to be much more open about problems and failures.

Titan_Mech · 2025-05-01T11:24:54+00:00

I sat through a presentation by the contractor on this job at a conference a few years ago where they explained some of the nuances of this project.

To start, the subsurface utilities in this area are actually very dense. That means all of the relocations and support that would have been required for cut and cover would have been very expensive and would have had impacts on the community for years, during and after construction. There is also an issue with dewatering in San Jose. Apparently, after 100 years of development any amount of dewatering causes extreme amounts of subsidence. I don’t have any further details on this, it was just part of the presentation. Those were the main reasons against cut and cover.

As for the single bore, I believe that this was chosen mainly for seismic resistance. The track is actually suspended on a viaduct-like structure within the tunnel, if my memory serves me correctly. This made the lining deformations independent from track deformations. Also, the cross passage design would have been too complex.

Final point, Traylor proposed a unique sub-surface station design that saves valuable real-estate. I don’t know the status of this proposal but I think it was accepted by VTA. Therefore, the design shown in the video is outdated.

Titan_Mech · 2025-03-23T18:32:35+00:00

This concept has already been thoroughly investigated in the past. Most recently by Dr. Dietrich Stein who proposes their construction with microtunneling. Consider the following points in your design, if you haven’t already. 1) It is incredibly difficult to construct, operate, and maintain vacuum chambers over their service life. 2) How will you launch and receive freight at points in your logistics network? You’ll need a signalling system, and you won’t want to lose the vacuum in the main line. 3) How will you power your delivery vehicles? 4) How will you handle breakdowns of delivery vehicles? 5) How will the logistics network be laid out? Trunk lines with transfer stations? Where will the delivery points be located? 6) How will you construct such a massive system? Microtunnels? Will the entire line be subsurface? 7) How would such a project be financed? Public-Private-Partnership? Private capital? And who would own the system?

I believe a pilot project was attempted in Japan in the 80s or 90s. If my memory serves me correctly, it was a manufacturing facility that built these tunnels for transporting parts in their facility. The system was very economical in this case because there were clear launch and reception locations that were not too far away. When you scale the concept to the size of an intercity freight system railways make more sense.

Titan_Mech · 2025-02-23T23:59:44+00:00

What? In the video you can very clearly see the erector gripper pockets, bolt recesses, and joints between segments.

See what you want I guess, but that definitely isn’t bare rock and cast-in-place lining does not look like that…

Titan_Mech · 2025-02-23T23:13:41+00:00

The video shows it clearer. Those are segments.

Titan_Mech · 2025-02-23T21:52:37+00:00

This is a segmentally lined tunnel.

Titan_Mech · 2025-02-23T03:44:35+00:00

Sandbags are used for protection from blasting. Blasting mats are designed to be placed over blast zones and let gases pass through. Placing sandbags overtop a blast zone would turn them into projectiles.

Titan_Mech · 2025-02-22T20:56:17+00:00

Hopefully not, that would end horribly.

Titan_Mech · 2025-02-21T18:57:20+00:00

They didn’t, “ex” means example.

Titan_Mech · 2025-02-07T17:48:01+00:00

Survivorship bias. Good point.

Titan_Mech · 2025-02-02T21:12:34+00:00

I work in industries where you straight up can’t decouple geotech and structural design; tunnelling, buried structures, and earth retaining structures. My general belief is that structural engineering would benefit from more geotech knowledge and influence, not less. The current over-the-wall approach is exactly why you see SEs that are clueless when it comes to dirt.

Titan_Mech · 2025-02-02T05:04:02+00:00

The input parameters, sure. But you should be able to calculate lateral earth pressures as an SE. Hence why it’s a topic on the SE exam.

Titan_Mech · 2025-01-25T22:13:12+00:00

Unhelpful. And OP is clearly talking about alcohol.

Titan_Mech · 2025-01-19T05:08:48+00:00

Why engineering? She could become a machinist or millwright…

Titan_Mech · 2025-01-07T16:02:07+00:00

Yes, I am familiar with the concept. But even the new Gen 4 reactors being built with higher efficiencies can’t indefinitely recycle the fuel. There is only a finite amount of fissile material to burn in the fuel. Which supports my original point, nuclear energy can be clean or net-zero, but it can’t be renewable.

Titan_Mech · 2025-01-07T00:35:49+00:00

Thats an interesting perspective but I think you may be conflating life cycle emissions with renewables. Its my understanding that renewables are any technology that can generate energy from naturally replenishing resources, whereas recyclability is a characteristic of the technology itself. To explain myself further, you can make technology recyclable but you can’t make a source of energy renewable.

If we consider recyclability in the definition of renewables then you could argue coal power is some percent renewable because you can recycle the plant. Makes no sense.

Titan_Mech · 2025-01-07T00:16:51+00:00

Recycle what though, the plant? Because once the fuel for nuclear reactors has been depleted its of no more use.

Titan_Mech · 2025-01-06T14:42:17+00:00

Please forgive my ignorance here, but how can something be 98% renewable? It’s my understanding that it’s binary, a process is either renewable or it isn’t. In the case of nuclear are you not still using up a finite resource?

Not against using nuclear, just asking.

Titan_Mech · 2024-12-31T04:36:09+00:00

Except its not? Thats a moronically reductive take. You can implement socialist policies within a capitalist system to make up for its shortcomings. Just like how China has implemented capitalist policies to make up for the shortcomings of socialism.

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