Passive Pressure against Grade Beam

[tclat]

Dear All,

I have structure supported on a piled foundation. The pile caps are tied with grade beams and the primary structural grid is 13'-0". My grade beams are between 2-3' deep. I am currently trying to resolve the lateral loads due to a seismic and was wondering if I could use the passive resistance against each grade beam. The general question is, at what distance does the passive pressure "dissipate" into the ground below so that it does not have an impact on adjacent structures.

Another scenario would be a "piggy back" retaining wall design. I know how to account for the bearing pressure from the upper wall on the lower wall but how does one handle the sliding force from the upper wall. At what distance does the passive resistance and friction force "dissipate" so that it does not have an impact on the wall below.

Thanks.

 

[fattdad]

the Rankine passive wedge is graphically shown as a right triangle with the hypotenuse (sp) running on an angle of 45+phi/2 measured from the vertical taken at the base of the grade beam (or footing, or retaining wall, etc.). Log spiral passive zone would be different (and would also return a greater value).

It takes a fair bit of movement to fully mobilize passive earth pressure. You'd need to also check the p-y relations of the pile against the soil. It's been a couple of decades since I worked on this, so I'm a bit rusty. That said, there are also inertia affects (i.e., the the reversal of seismic energy will not coincide with the building's response).

f-d

¡papá gordo ain’t no madre flaca!