calculation of slide downward soil load on piles?

[RobertEIT]

It might be a very simple question. But..., too many various kinds of tricks make me nervous. I would like to make sure there is no tricks in calculating the slide down soil load on piles. Please see attached word document, is vertical load of soil on the pile simply equals 9.49 kips?

Thanks a lot.

 

[Teguci]

I suppose I would first suggest you change your sketch to show a point load acting upon the pile and not through it.

If the point load acts on the pile with a 30 K force at the 3 to 1 angle then yes, the vertical component is 9.48 K. The bigger problem is that the lateral component is 28.5 K.

 

[Ron]

Well....not quite. The soil doesn't act like a solid object gripping the pile and pushing downward. The only thing that mobilizes the downward load on the pile is the friction between the soil and the pile. Further, your sketch implies a long distance of soil influence on the pile. That's usually not the case. If the pile were a retaining wall, then you would have a sloping surcharge condition. Since the pile is relatively small compared to the soil mass, the influence is not as clear nor as large.