Critical depth for end bearing piles
Critical depth for end bearing piles
(OP)
The COE's Design of Pile Foundations lists a critical depth, 10 to 20 pile diameters, beyond which end bearing does not increase. I cannot understand why this would be applied to end bearing.
Engineering is the art of not constructing...of doing that well with one dollar what any bungler can do well with two after a fashion.





RE: Critical depth for end bearing piles
RE: Critical depth for end bearing piles
page 19
b. End Bearing
For design purposes the pile end bearing capacity can be assumed to increase linearly to a critical depth (Dc) and then remains constant. The same critical depth relationship used for skin friction can be used for end bearing.
Dc=10B for loose sands
Dc=15B for medium sands
Dc=20B for dense sands
3. Piles in Silt
page 20
b. End bearing
The pile tip bearing capacity increases linearly to a critical depth (Dc) and remains constant below that depth. The critical depths are given as follows:
Dc=10B for loose silts
Dc=15B for medium silts
Dc=20B for dense silts
Engineering is the art of not constructing...of doing that well with one dollar what any bungler can do well with two after a fashion.
RE: Critical depth for end bearing piles
HTH
VOD
RE: Critical depth for end bearing piles
To develope full point bearing capacity, the soil has to remain under the pile point cross section. Until the pile is "deep" enough there is insufficent pressure from the depth of soils (head) above the point to provide confinement. In other words, at shallow depths the soil under the point "squirms out of the way" when loaded - the result being settlement.
Critical depth increases as the sand or silt gets more dense. This seems to be the opposite of common sense. However the more dense the sand or silt, the less that it acts like a "fluid" which can exert the equivalent of a "hydrostatic head" to provide confinement.
RE: Critical depth for end bearing piles
Engineering is the art of not constructing...of doing that well with one dollar what any bungler can do well with two after a fashion.
RE: Critical depth for end bearing piles
You seem to be well aware that engineering, and especially pile driving, are a mix of both "science" and "art". After becoming a PE, I had a six year career as a bridge and heavy construction contractor in the 1970's - we practiced the "art" of pile driving - most of it in the silt and sand in the South Carolina low country. That is when I learned the explanation that I gave you.
Times change, and I will certainly yield to advancements in "science".
Thanks for letting me know, I have downloaded his paper and will read it carefully.
RE: Critical depth for end bearing piles