Depth finder for ground imaging

Hire it done, with a "hard-dig" clause in your favor... you should hear the noise when you blow a hydraulic hose on a Michigan end loader ;-)

...Jim Thompson

Graham

What's the soil like that isn't the BFRs[1]? The depth finder will see a very large contrast at the water to soil transition. This is likely to make the idea unworkable.

GPR won't work in wet clay soils.

Seismic is too much of a blunt instrument for this sort of problem.

If the BFRs are rare enough and the soil is otherwise uniform enough, a simple resistivity system may work for you. You would just avoid any place with a differing resistivity.

You may be able to find the rocks magnetically also.

Many years ago I tried to detect caves using this technique. It didn't work, soil is a pretty poor medium for conducting sound at any frequency.

Ken Smith wrote: (snip)

(snip)

In my industry, "BFR" means a very-large-value resistor. :-)

Soil is glacial drift gravel with lots of baseball sized rocks and smaller. BFR's are Canadian Shield granite boulders. Path is 75 feet from the edge of a lake, so with the gravel, I would expect a high water table which should help. And I can flood an area before starting to ensure adequate saturation for signal propagation.

I suspect you are just going to have to start digging and find your way past the rocks. Glacial till is a highly variable material. You will have a hard time telling, lets say, a pocket of sand from a BFR.

Assuming this echo sounder works at a highish frequency, a mixture of sand, rocks and water will just eat any signal that gets into it. Most of the energy will reflect back at first bit of rock it hits.

Remote sensing technologies tend not to have enough resolution for this sort of job. I'd try GPR before I gave up because it may work.

In article , bruce varley wrote: [....]

Anyone who lives in earthquake country knows this isn't true. The energy in an earthquake is sound.

Also, there is an entire seismic industry based on the fact that soil is a good conductor of sound.

I've always used "BMF", which is actually an adjective and can be applied to any large unwieldy object: BMF rock, BMF cap, BMF hammer, etc. ;-)

Cheers! Rich

Do you have enough water to actually wash the gravel away from the BMR's, and just haul them away? (and check the tailings for gold nuggets and gemstones. ;-) )

Good Luck! Rich

So stick a bunch of microphones in the ground, and wait for an earthquake. ;-)

Cheers! Rich

The primary conduction is probably through rock, not the soil on top of it. Also earthquakes and even seismic sounders are pretty "loud" to being with.

To solve the original problem, how about drilling a core every few feet along the path? Commonly used when siting buildings to figure out what they are going to be built on/if they'd have to blast bedrock to finish the excavation.

Get a piece of tube, maybe 6' long, and connect high-pressure water to one end of it, and use the other to shove through the loose gravel until you hit something big.

Good Luck! Rich

In article , Rich Grise wrote: [....]

They're called "geophones" when they are stuck into the dirt.

This exact experiment has been done a lot of times. They have also stuck them into the ground and just listened to the random noise of wind hitting the trees etc. With enough CPU power, you can make something out of the data.

You missed the entire "refraction" market. They are looking at the near surface stuff and the signal source is a person with a big hammer. Seismic sounders are mostly in the oil industry. They cost way too much for the guy bidding on making a road to afford.