Point Load Distribution

[EntryLevelEIT]

Hey fellas,

Just looking for some insite on how a point load distributes through earth. Please see the attached pic and let me know if it seems correct or not.

 

[nutte]

A simplified method is to use a 2:1 distribution (2 vertical to 1 horizontal).

http://www.ce-ref.com/soil_stress.htm

 

[amecENG]

Research Boussinesq Equation where a point load creates a stress bulb in the soil

 

[BigH]

You can find all you ever want to know in Poulos and Davis' book Elastic Solutions for Soil and Rock Mechanics. You can google it and download it from the net.

 

[msquared48]

EntryLevelEIT:

You also posted the same question in the Civil Engineering Other Topics Forum where I had to red-flag it to be removed - Double posting the same subject is not allowed.

FYI, you might get more responses in the Geotechnical Other Topics Forum as the subject is more suited for that forum. If you desire to post there, redflag this string and put your question in the other forum.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[rscassar]

I think the 45deg you have used to be a good assumption. There are equations out there that calculate stress bulbs but I think your assumption is good. All the load will be accounted for.

Is this the lid of a buried sewer or tank? If the point load is a traffic load it may require dynamic magnification because of the depth of soil profile.

 

[BigH]

Disagree with kikflip - it is standard and traditional if you use an "angle" to use 2V:1H. Terzaghi, Bjerrum, et al used it - who am I to argue?

 

[BAretired]

I agree with 2V:1H, but would point out that you cannot have a concentrated load on two feet of soil. It would sink through like a knife through butter. There has to be a bearing area at the surface.

BA

 

[rscassar]

Who am I to argue. 2V:1H it is.

 

[csd72]

Yes, I definately would not use 45 degrees for soil, for concrete yes, but not appropriate for soil.

2:1 or approximately 60 to 65 degrees from horizontal is the accepted spread that I have used for tunnels under highways.

This information should be available in your local bridge code.