Soils Question from a structural engineer

[Luke2020]

Hi all.

I have a question that has no doubt been covered on this forum but I can’t find a solution.

Does tabulated data exist covering the angle of dispersion through different soil types?

I am to believe (depending on what is being checked, i.e settlement etc) that the angle is 30 degrees to 45 degrees. Is this 30 degrees from the vertical ( or 60 degrees from the horizontal as shown).

I have a gravity retaining wall in bed rock and I’m trying to argue a steeper load angle through the ground beneath to avoid an adjacent structure.

Any opinions, discussion or assistance as always is welcome.

Luke

 

[jayrod12]

Better dust off your old soils mechanics books. Yes, it differs depending on the soil strength. Generally speaking if it is bedrock, you probably aren't really needing to rely on load spread. So I'm not sure the issue.

 

[Luke2020]

I took Craig's soil mechanics from propping the door!

This is more for general understanding. The SI states dense sand (probably weathered bedrock)

For future reference I'm trying to understand the behavious of different ground types.

 

[GC_Hopi]

The 2:1 rule is pretty common for depth to radial distance. A good reference for depth of influence is Terzaghi. Here is a sample from one of his books.

 

[Luke2020]

Thanks GC bu till be perfectly honest i dont quite follow that above.

I have always used and assumed 45 degrres. But I am lead to believe that is conservative.

For my current problem I want to change this angle of influence to avoid a nearby property and being in bed rock I feel like this is fine, (but have nothing to back to this up so obviouslty wary!)

 

[Sebast73]

Hello Luke,
is the material beneath native, compacted fill ?
Sand and Gravel = more like the 45 deg.
If siltly / clay = more like the 60 deg. from horiz.

You prob. know this much, but maybe it helps. Anyway I am a firm believer in if you need or want assistance, it is beneficial to offer your help for some other in need of assistance,

There are many texts which give varying interal angle of friction for varying soil types.

 

[Sebast73]

Attached is a typical chart showing different angle and soil types in varying conditions
Also included the following link. hope it helps.
Link

 

[Sebast73]

oops forgot to include the file here it is attached

 

[r13]

I have a gravity retaining wall in bed rock

Any of above method of spread pertaining "bed rock"? Just curious. I think at least the properties and condition of the rock need to be addressed.

 

[PEinc]

I’m trying to argue a steeper load angle through the ground beneath to avoid an adjacent structure.

Is the top of the foundation for the adjacent structure above or below the bottom of the gravity retaining wall?

http://www.PeirceEngineering.com

 

[Luke2020]

Thanks all

The image below will hopefully clear a few items up.

I am interersted in the spread from the existing retaining structure highlighted yellow to the new basement retaining structure. this is the permantnt solution but also for the temporary works (which is a more complicated hing in itself and could sparka whole new conversatino)