45 degree bearing splay of foundations?? 1

[jtjt]

i have been told different thingd. on what part of the footing do you start your 45 degree angle, is it measured from the top of footing, the bottom of footing. i have even heard 9" from the top of footing? just wondering of there is a link or code somewhere that i can print out.
Thank you to whome ever can answer this for me.

 

[BigH]

Normally, for spread of loads with depth (stress) one uses 1H:2V. When a footing is near a slope, one typically uses 30 to 45deg from the horizontal from the bottom of the footing. When one is placing footings at differnt levels, one normally uses a spread of 2H:1V. Varghese says in the latter case that the bottom of the footing (lower footing) would be 2H:1V in sands but in clays, the 2H:1V would be to the top of the footing. (likely an Indian Standard).

 

[jtjt]

what about for overexcavation against an existing building.we would be slot cutting along the building but i am going to make my removals down to our BEP then do my slot cuts. its a silty sand that has been processed and compacted about 9 years ago.Not sure if they will have us slot cut once we have the slope agains the building exposed but i want to make sure i have that slope cut made properly. dont want to leave any excess or cut to much.
thanks so much for your respons.

 

[hokie66]

The extent and sequence of excavations allowed adjacent to an existing building should be defined by the designing engineer, in consultation with the adjacent building's owner.

 

[jtjt]

the building is on the same property,
I have always carried my cut from top of footing to play it safe, since i do this for slot cutting it hasnt matterd since i will remove it all anyways. since in this situation i may not have to slot cutt i thought i would ask all you enineers out there if you knew what the actual lateral support was measuring off of the existing footing. top, bottom, middle of footing ect.

 

[msquared48]

The footing does not transfer bearing stresses to the soil at the top of the footing, only the bottom. So the line, at whatever angle is appropriate for the bearing strata seen, starts from a bottom corner of the footing.

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

 

[csd72]

But this is no guarantee that you will not affect the footings this is just a minimum.

Not sure what slot cuts or BEP are so I cannot comment further.

 

[dicksewerrat]

I always thought that you used the angle of friction of the material you are building on and from the bottom of the footing. Most of the time that is between 32 degrees and 39 degrees.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com