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Thread: trying not to steal a topic here

  1. #1

    Default trying not to steal a topic here

    The recent posts on railroad tracks had me thinking of an old idea. The purpose of this post is NOT to get political, but to get some insight on what I though was a really good idea.

    I thought that, instead of a border wall, there could simply be a set of RR tracks. The tracks serve two purposes. One, to carry several ground penetrating radar cars doing comparison sweeps for tunnels, and two, the tracks carry a continuous train (forgive the pun) of low-power TDR pulses to detect impedance changes from, say, a person crossing it (likely originating from the same radar cars). Sure would be easy to know where and when someone or something crosses with such a setup. Certain prisons do something similar weaving parallel wires through their perimeter fences. I'm hoping there are people here that can logically shoot down the idea so I can give up on it and move on. Why wouldn't that work?

  2. #2

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    I'm thinking it would be less expensive to build and maintain the wall than it would a railroad. Because of of how friction works with steel wheels on steel rails, most railroads avoid grades higher than about 2% with 2.5% being the highest. By comparison a lot of mountain highways have grades of 6% or better. To maintain a 2% grade, a railroad will meander, have a lot of tunnels and a lot of cut and fill grading on the route. There's an old railroad line built in the early 20th century that runs from San Diego out to El Centro in the desert. Because of the grade requirements, part of the line was actually built in Mexico because the US side of the border was too rugged. By comparison, the border fence that runs from San Diego east follows the contours of the land.

    The other thing that makes the wall more economical is that railroads require constant maintenance. The pressure of the heavy loads running over the tracks causes a lot of wear and tear on both the track and the rolling stock. Maintenance costs are very high and ongoing.

    The rail line I mentioned above is more or less intact on the US side of the border and the Border Patrol has a Hi-Rail vehicle (a truck with wheels that allows it to run on the tracks in addition to the roads) they will put on the tracks to patrol the border area. In addition, the BP uses ground sensors that will detect persons moving about in the area of the border. (I trained with those type of sensors in the US Navy during the Vietnam war. Pretty cool stuff...)

  3. #3

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    Good points. Terrain, it didn't even cross my Minnesotan mind. Although its now moot, the track wear I'd be less concerned with. I wasn't suggesting repeatedly hauling taconite or anything heavy on the tracks. A few radar cars would hardly keep the rust off them. But, I agree overall. I also agree with your ground sensor comment. A long time ago I did a few experiments with detecting ground movements after a few odd trembles nobody else seemed to notice here (turns out, minnesota has little fault lines, many of them, and they can sometimes be heard if you live in peaceful-ville like me). I only got as far as a speaker with a counterweight but it would detect distant trucks and helicopters 5 feet down in the clay hill we are on. At night, I hear vehicles 3 miles away indoors while in bed but can't hear a thing stepping outside. Something about the clay and rock below and the deep pillars this cabin is on...

    Does desert sand carry sound like clay on bedrock does?

  4. #4
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    Quote Originally Posted by brandon lind View Post

    Does desert sand carry sound like clay on bedrock does?
    no due to the air spaces between the grains of sand any sandy soil would simply muffle sound unless it has been severely compressed.
    even though quartz is a good sound conductor but only if it is solid.
    clay being more dense passes sound vibrations but not very efficiently
    rock on the other hand readily passes vibrations and therefore sound.
    the more crystalline the rock is allows for better vibration transmission.
    ( example quartz and granite compared to shale or slate) shale and slate being on the low end of a scale.
    too much blood in my caffeine system.

  5. #5

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    Im getting off topic with the original post here, but with respect to the sounds that propagate through this clay, I thought it worth sharing what got me interested in listening deep down. There were 2 distinct times I felt what I thought was a distant earthquake, both within 1 week of each other roughly 4 years ago. I live in northern Minnesota where earthquakes are almost unheard of, but after digging around, I learned there are several faults in MN. On one occasion the stuff in the cabin rattled for 3 seconds late at night (when no blasting occurs - mines 44 miles from here) and on another occasion I was in the boat one morning, and suddenly, all around the boat and along the shoreline as far as I could see, there was a sudden instantaneous release of gas bubbles from the lake bottom (gas from plant decay builds up in the muck). I read of one local quake in December of 1923 that was in Bowstring MN (only about 5 miles from where I am) in which a house reportedly swayed in an east/west direction. There is nothing on record with the USGS during the time I noticed these events, but if you say clay is less than excellent at propagating sound, I'm very curious what happened 4 years ago. I know there is a large amount of basalt under MN, and often wonder if that channels noise from the New Madrid area up the mid-continental rift like an audio duct, but all that is a bit too far east of me to explain what I felt.

    Forgive me, I'm a Minnesotan. If I were from California, I would not be so excited about stuff like this lol. I drifted way off point as soon as K6CPO mentioned ground sensors

  6. #6
    gnuuser's Avatar
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    Quote Originally Posted by brandon lind View Post
    Im getting off topic with the original post here, but with respect to the sounds that propagate through this clay, I thought it worth sharing what got me interested in listening deep down. There were 2 distinct times I felt what I thought was a distant earthquake, both within 1 week of each other roughly 4 years ago. I live in northern Minnesota where earthquakes are almost unheard of, but after digging around, I learned there are several faults in MN. On one occasion the stuff in the cabin rattled for 3 seconds late at night (when no blasting occurs - mines 44 miles from here) and on another occasion I was in the boat one morning, and suddenly, all around the boat and along the shoreline as far as I could see, there was a sudden instantaneous release of gas bubbles from the lake bottom (gas from plant decay builds up in the muck). I read of one local quake in December of 1923 that was in Bowstring MN (only about 5 miles from where I am) in which a house reportedly swayed in an east/west direction. There is nothing on record with the USGS during the time I noticed these events, but if you say clay is less than excellent at propagating sound, I'm very curious what happened 4 years ago. I know there is a large amount of basalt under MN, and often wonder if that channels noise from the New Madrid area up the mid-continental rift like an audio duct, but all that is a bit too far east of me to explain what I felt.

    Forgive me, I'm a Minnesotan. If I were from California, I would not be so excited about stuff like this lol. I drifted way off point as soon as K6CPO mentioned ground sensors
    heres an interesting experiment to try!
    dig a hole down to the solid clay and drive a 1 foot rod into it, then tie a piece of heavy fishing line to the rod.
    place a plastic sheet over a plastic barrel with the ends cut out and place it over the hole with the fishing line rising up through the center of the plastic and a large button draw it snug like a drum.( cut a hole in the side of the plastic barrel to allow you to tie the fishing line) this will make a ground "speaker"
    you will be surprised how sensitive it is.
    too much blood in my caffeine system.

  7. #7

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    awesome idea, theres a guy selling plastic barrels 20 miles from me. Ill try that this summer!!!!!

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