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Radius of foundation influence

Radius of foundation influence

Radius of foundation influence

(OP)
When excavating near a building how do you determine the radius of foundation influence so as not to undermine the building?

RE: Radius of foundation influence

Boussinesq and Westergaard have equations for horizontal and vertical stress distribution with depth and distance from the point of loading (or the area of loading).

use those equations.

f-d

¡papá gordo ain't no madre flaca!

RE: Radius of foundation influence

You know you're too close when the adjacent property owner starts taking pictures.  bigsmile

Mike McCann
MMC Engineering

 

RE: Radius of foundation influence

msquared48 - even if you are not "that" close, a smart owner will take pictures! There are a number of figures in various texts and such that show the angles that should be used . . . my books are now packed for move - but will try to put my hands on one.  Comes to mind - 45deg from bottom of existing footing down to yours - or vice versa if yours is higher.  I wouldn't put footings any closer than 2B if at same level.  Too, a lot depends on the type of foundation material you have.  If on rock - then most of this is "mute".  If on clays, you may need to be a bit more conservative.  If on sands, the influence of the new footing will not be as great on the old as if they were built at the same time.

RE: Radius of foundation influence

I agree with Big H, 45deg from bottom of existing footing down to yours.  However, the soil/rock type will have a significant impact on the answer to this question.   

RE: Radius of foundation influence

Do the homework dmev.  The equations can be found in NAVFAC DM 7.1.  Plenty of equations to determine the stress at a point from a line load, column load or whatever.   Make spreadsheets out of it and charge client lots of money.

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