The diameter of the concretions and rocks are ~ 10 to 20 cm at depth of 1 to 3 meter under a salt marsh environment. The salt marsh sediment generally has very high moisture content with 30% of clays. Attached is the photo of the salt marsh environment.
Hi Chin,
Can you give us a depth estimate and what is the survey area?
Cheers
Chris
Dear Christopher,
The estimated depth is within 1 to 3 meters. We haven't decide about the survey area yet (say maybe around 200m2). At now, we just want to know if there is any method or suitable handheld device to do the job. Thank you very much.
Cheers,
Chin Yik
It is a tough one, because electromagnetic methods such as GPR don't like salt water and even less when combined with clay, but you could probe the subsurface with a penetrometer, although you may need to build statistical density models... If I think of anything else, I'll let you know.
Chris
Have you considered an acoustic imaging approach as used in seismic surveys?
Regards,
Ray
Thank you very much for the questions and suggestions. We intent to map out the concretion in field very fast. Just to get a brief idea where the concretions are. Therefore, we are looking for something handheld or something that can get the results real fast in the field..
You need an acoustic echo sounder at least 10 kHz in frequency, preferably higher.
These are commercially available and your choice will depend upon how you intend to power and deploy it. They are sometimes available for rent.
If you want a quick low tech solution you could use a rod probe (commercially available or make your own) which you can push through soft soil until you hit rock. Alternatively, if the clays is too stiff or too deep you could use a small diameter hand auger or a dynamic cone penetrometer. Both typically come with extentions.
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