Chinese engineers wire Raspberry Pi into 600-meter railway tunnel to find any holes Chinese scientists have found a novel use for the Raspberry Pi: detecting voids in the linings of railway tunnels that could lead to structural damage, or even collapse. News of the Pi's potential new role appeared last week in the journal Buildings – the organ of the International Council for Research and Innovation in …
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Everyone knows what is meant but still seems a little redundant.
A filled void presumably would no longer be a void.
The authors suggest machine learning could be applied to the collected sensor data, or even to build digital twins of tunnels and allow real-time decision support. They would say that wouldn't they. :) Grant application to follow..
I wouldn't have imagined concrete would be sufficiently conductive to detect an air filled cavity in it. I would have punted on ultrasonics where air/concrete interfaces should strongly image.
Concrete itself is not particularly conductive. But as my mother explained to me as a child* concrete is porous, and the pores become filled with water, and ions, and thus effectively conductive.
*There was an incident involving my younger brother, a long wire, our boat, the boat-motor's secondary ignition circuit, the cement garage floor, and me, despite wearing insulative-soled tennis shoes, receiving enough voltage to result in me taking an unscheduled lie-down.
The article says that they embedded wires into the concrete - my reading of that is that they are running a current through those wires, not the concrete itself. If there is a void that has been successfully filed with grout, there is little current loss, because the concrete has low conductivity.
If the void is not fully grouted, I would generally expect that it would be water filled, not air filled (not always the case, but there is generally groundwater around tunnels), and that would cause current leakage where the wires pass through the void(s).
Still, it's all a variant of geophysics, which is a dark art involving clever physics, black boxes and the odd sacrificial chicken.
Agreed, but a Raspberry Pi seems a bit of overkill for the situation too. Unless they meant a Pi Zero or something. I'm sure someone could knock up a simpler and cheaper alternative with far less complexity. It's an interesting and useful concept nonetheless.
I remember simple circuits from the likes of Everyday Electronics, Practical Electronics et all which these days would almost certainly be developed with an Arduino or similar with a software stack instead of a few passive components and a soldering iron :-)
Knowing a little about the many tunnels under our London. Soil is surprisingly fluid and some of the tunnels have considerable flex to them, rising and falling in the fluid. Monitoring for voids and/or overpressure are critical maintenance activities. We semi-regularly need pump grout into the linings to stabilise. Many of these tunnels are over 100 years old; and certainly had little thought to condition monitoring at the time of install. But engineers are clever folks and simple pressure monitoring goes a long way.
Tunnels may seem to be a panacea for the NIMBY brigade when it comes to trains, power lines and pipes; but the costs involved in upkeep are astronomical.
Really deep tunnels in rock obviously carry different issues, but then, your cost of installation goes up even higher.
The digital twin side of the world is just marketing BS; you collect data and set a policy up to act upon it. Level goes above or below defined threshold X? Open the pressure relief and/or pump in the grout. Or, if you are irresponsible, you just let them fester...
Having built several systems that would be called "digital twins" these days...
Yes, absolutely. They make for an impressive looking demo, but are utterly useless for actual maintenance of the site.
But they demo well, so it's apparently worth spending the budget again for the pretty pictures that nobody looks at after the first couple of weeks.
"Tunnels may seem to be a panacea for the NIMBY brigade when it comes to trains, power lines and pipes; but the costs involved in upkeep are astronomical."
For transportation, the typical cost starts with installations on the surface increasing with elevated and finally with underground being the most expensive. For a city such as London, they are out of the first two and have been for some time. For HS2, the system is a combination of all three and then some all combining to maximize build cost. I agree that ongoing costs would seem to be the most expensive for underground. Just access to repair something is usually a full shut down and then an enormous amount of specialized machinery to do the job since it all has to fit down the tunnel and be able to do the job when it gets there.
Just as some think that 15 minute cites are the answer to efficient living, I believe that too much density creates issues that can never be solved given how irrational people can be. Big cities tend to also not be planned, they just sort of evolve over time so transportation and other services are bolted on as/where. I'm wondering if sewer tunnels are going to wind up a 100m down or built to operate at high pressure to convey the added volume as big cities are made bigger. Hey Ginnie, I'm ready for my escape to the country.
"Everyone knows what is meant but still seems a little redundant.
A filled void presumably would no longer be a void."
Yes, but what do you call a void that has been filled? A "filled"? A "no longer void"?
There may be specific words that are used to indicate a void that hasn't been filled (yet) and a previous void that has been filled, but people outside the business might not know what they mean. It can also be important to know that a location was a known void that was filled during construction in case that information is important later.
If they kept the data on their own, Internet-connected computer, it could be "remotely accessible" if they wanted it to be.
I'm tired of seeing/hearing remote access being used as a pro-cloud selling point/excuse, as if non-cloud computers were incapable of providing remote access.
I’d be surprised if they’re using SD, it was the nice and cheap way for school children to do things using these boards a decade ago, there was little expectation the cards would last long enough to hit the rewrite limit!
My 'do useful things' bunch of R-PI4s all boot from M2 SSD sticks in tiny USB enclosures.
To get the data to the "cloud" from inside a tunnel will require wires to get the data to the outside world, where it will most like go down a fibre or copper link or possibly even a wireless data link. At which point, you can connect to it directly yourself, no need to store it on someone elses computer in a cloudy bit barn.
Idiot.
Indeed.
@irongut.
Are you 18 and just started in IT or are you such an "idiot" that you think if it's remote it has to connect to the cloud?
Not sure how we ever survived before cloud. I must of travelled at least a million miles a year collecting information of remote devices ..oh wait, no I didn't.
Pin 2 is 5V, Pin 34 is GND. Ok, we are now running a very small current through the concrete. What are we doing for measurements? None of the GPIO pins are analogue, they are all 3.3v logic (not 5V!).
So, is it a simple potential divider incorporating the concrete as one arm? Or an actual A/D converter?
Amazingly, the paper seems to imply that you can measure the current flowing in the 5V supply. I can see no documentation to that effect. The paper reads like the author does not really understand what's going on.
> ...or the person writing it up was only given very partial details.
elReg writer Simon cleverly linked the actual article for you to reference. It is 12k words of quite fine English, properly sectioned also searchable, with pictures.
You pin-fans really want to read section 4.2 "PINs Used in This Study". In addition to a Pi there are several types of sensors. Repeating all this readily available description would not improve Simon's article or paycheck.
This appears to be a tool for installing or adding grout, to know when you can stop the grout mix-pump; not an ongoing monitor. The paper's authors knew what they were doing and were writing for others in the industry, and I concede that they skimp some obvious (to them) details.
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