1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Geotechnical question

  1. Nov 29, 2008 #1
    What capacity should be maintained to not float a 500-gallon plastic septic tank under groundwater-caused buoyancy? What other external installation steps should be taken to prevent floating. It rains a bit in Houston. Thanks.
     
  2. jcsd
  3. Dec 3, 2008 #2
    If the tank is right at the ground surface, and flooding may occur to the ground surface, then it would need to be kept full to not float.

    I assume the top of the tank is 4 feet or below below the ground, This earth cover helps prevent flotation, even when entirely submerged. to determine likelihood of flotation, an engineering approach is to determine the safety factor; the resisting forces divided by the uplift forces. You would like to have a SF of at least 1.1 under worst conditions.

    Uplift forces:
    -tank outside vol x 62.4 pcf (if fully submerged)

    Resisting forces:
    -weight of soil over the tank (if submerged, effective soil unit weight is approx 100 pcf - 62.4 pcf)
    -weight of tank & contents

    To increase resisting forces, you could pile soil higher over the tank, construct a concrete slab over the tank, use concrete or other deadmen below/along tank with straps over the tank, etc. Helical anchors & straps another option.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Geotechnical question
  1. Question on torque (Replies: 1)

  2. A matlab question (Replies: 4)

  3. Comsol Question (Replies: 1)

Loading...