Results 1 to 10 of 10
Like Tree1Likes
  • 1 Post By Mke

Thread: How to do this? GPR?

  1. #1
    Junior Member
    Join Date
    Apr 2011
    Location
    Asia
    Posts
    19
    Years of Experience
    1
    Rep Power
    7

    Default How to do this? GPR?

    Hi, can someone suggest what type of instrumentation needed for the following task:

    We want to measure the harden clay sediment accumulated at the bottom of concrete tank, as it is, we can only access the top of the concrete tank (flat surface) and with limited openings at the top . In essence we have, a layer of concrete at the top, a layer of void (air) below it, water, harden clay, and another layer of concrete at the very bottom. Top to bottom depth is approximately 8m. The tank is normally 3/4 full and the sediment thickness varies from a centimeters to 2m..

    Just wondering if GPR or such equipment can be used, would appreciate some suggestions too..

    Thanks in advance for reading & responding..

    ard

  2. #2
    Junior Member
    Join Date
    Sep 2012
    Location
    md
    Posts
    8
    Rep Power
    0

    Default Re: How to do this? GPR?

    I don't think for would work for that,,not the one I used anyway

  3. #3
    Senior Member sauroke's Avatar
    Join Date
    Sep 2010
    Location
    Under Heaven's Skies
    Posts
    182
    Years of Experience
    10
    Rep Power
    15

    Default Re: How to do this? GPR?

    No, it won't be able to tell the difference between clay and concrete.

  4. #4
    Mke
    Mke is offline
    Senior Member Mke's Avatar
    Join Date
    Oct 2008
    Location
    Republic of Washington
    Posts
    1,536
    Years of Experience
    16
    Blog Entries
    34
    Rep Power
    77

    Default Re: How to do this? GPR?

    uhhh, a good antenna on a good GPR could tell a difference between hardened clay and concrete. The issue you are going to have is any reinforcement in the concrete lid. Your signal will get bounced around and it may have difficulty showing the underlying layer of clay.

    Why don't you just hand auger through the clay layer in the tank to figure out the depth of the clay? Cheaper and quicker then a GPR team.

    Mke

  5. #5
    Junior Member
    Join Date
    Apr 2011
    Location
    Asia
    Posts
    19
    Years of Experience
    1
    Rep Power
    7

    Default Re: How to do this? GPR?

    Thank you for all the responds. It looks like GPR is not the tool.

    Mike,
    <<Why don't you just hand auger through the clay layer in the tank to figure out the depth of the clay? Cheaper and quicker then a GPR team.>>
    The concrete tank is big and there are limited openings at the top and at most time it is filled with water. No access inside the tank is allowed, which means the auger needs to reach at least 7 to 8m from the top to reach the bottom, can hand auger do this?

  6. #6
    Mke
    Mke is offline
    Senior Member Mke's Avatar
    Join Date
    Oct 2008
    Location
    Republic of Washington
    Posts
    1,536
    Years of Experience
    16
    Blog Entries
    34
    Rep Power
    77

    Default Re: How to do this? GPR?

    To be honest, with that much depth, I would use a professional driller. The hand Auger in theory would reach, the bad part is there would be multiple extensions on the rod and the torque used to go through the clay would likely twist the extensions to the point of breaking. A proffessional drill rig would be able to do that depth with no issue, as long as they had their auger or push probe with locking extenstions so they don't lose their bit.

    mke
    Newbie likes this.

  7. #7
    Senior Member sauroke's Avatar
    Join Date
    Sep 2010
    Location
    Under Heaven's Skies
    Posts
    182
    Years of Experience
    10
    Rep Power
    15

    Default Re: How to do this? GPR?

    Actually, MKE, it won't tell the difference with the layer of concrete. It will tell you the concrete is there at the top, possibly the void, but once it hits the clay, you are pretty much screwed. It depends on the salinity in the ground, what type of clay, etc.
    how big is your tank, 500 gallons? Measure the length, and width of the interior. Use a stick to measure down how far the clay is, calculate how much room is needed in height to give you 500 gallons, then subtract the height of the clay, it should give you the answer.

  8. #8
    Mke
    Mke is offline
    Senior Member Mke's Avatar
    Join Date
    Oct 2008
    Location
    Republic of Washington
    Posts
    1,536
    Years of Experience
    16
    Blog Entries
    34
    Rep Power
    77

    Default Re: How to do this? GPR?

    Sauroke, It sounds like a Concrete holding tank. If the hand auger needs to stretch 7-8 Meters.... Thats a Huge "F"ing tank. If it is poured in place there is no standardized shape so measure downs will do you no good.

    As for the the difference in materials.... Are you saying there is no difference between "hardened Clay" and concrete? There are variables to take into account, but typically concrete and hardened clay should absorb the signal differently. Especially in a tank that has water most of the time.

    mke

  9. #9
    Member KaineF's Avatar
    Join Date
    Jun 2011
    Location
    oklahoma
    Posts
    71
    Years of Experience
    4
    Rep Power
    9

    Default Re: How to do this? GPR?

    just use a long metal probe stick it in and when it hits hard stuff (clay) measure and when you cant pound it in any further you have found concrete remeasure and bam there you go

  10. #10
    Senior Member sauroke's Avatar
    Join Date
    Sep 2010
    Location
    Under Heaven's Skies
    Posts
    182
    Years of Experience
    10
    Rep Power
    15

    Default Re: How to do this? GPR?

    MKE, with no further information, we can only guess. If the water has an increased amount of salt, then a GPR is worthless. If the clay has been sitting at the bottom of the tank for 3 or 4 years, then it hardens, even with water. A high grade GPR may tell you the size, and possibly the depth, but even a cheap utility locating GPR is 10 grand. To have someone come out to do it, they will charge a minimum of 2 hours, no guarantee, and could run you up to at least 400.
    If the unit was installed, then there should be some record of the tank itself, especially by the manufacturer. To tell you the truth, without this information, you are still trying to shoot blindly to hit a duck.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •