Laterallly loaded piles 1

[Geotechnical76]

I understand that Broms method for laterally loaded piles assumes a constant subgrade reaction along the pile section. In cohesive soils, Broms assumed that the soil flows around the pile and based on that he assumed that the ultimate soil resistance will be [9(Su)(D)] (nine times the undrained shear strength times the pile diameter).The above estimate is good for short rigid piles.
The py curve method can be used for both short and long piles.

When the calculations from the py method and the Broms method are compared, results show large differences. For example, the Broms method suggested 15 feet of embedment to resist the lateral load while the py curve method suggested 33 feet. Concrete piles of 42 inches where used to resist lateral load of 50kips in medium stiff silty clay (cohesion=1000 psf).

Thanks.

 

[jdonville]

Geotechnical76

Reese and van Impe recently published a book regarding the analysis of laterally loaded single piles. I haven't made it through it yet, but perhaps there is something in there that could help you. Alternatively, the documentation for LPILE, or even the publically available documentation for COM624P could be helpful in explaining why the difference exists. You may also try to find a copy of FHWA-IP-84-11, as that has some useful discussion on the topic.

Jeff

 

[vulcanhammer]

From Pile Driving by Pile Buck:

"It is recommended that, for the design of major pile foundation projects, Reese's more sophisticated methods (p-y curves, etc.) be used. For small-scale projects, the use of Broms' method will yield generally acceptable results."

The documentation for COM 624 and the program itself can be found at

http://www.vulcanhammer.net/download/pile_driving_programs.php

 

[Touma59]

Geotechnical76

Could you please give more info. Water table present ? out of curiosity I used Lpile3 (Reese) with the info you have presented and a 15ft pile and it turns out to be quite adequate with insignificant deflection and a small moment. I ran the same example using our own software LatPile and I get a somewhat more conservative results (0.38in top deflection, 131 K-ft for the moment). Therefore, unless there is some missing info, the 50 kips should be easily handled by the 3.5ft dia and 15 ft deep, pile, embedded in stiff Clay. If I have to guess, I would say that your selected PY curves were a bit too conservative, because at the end, regardless of the approach, it is your selection of the soil springs that controls, and from experience, a carefull selection would reduce the difference between the various methods to less than 20%.

all the best

Tsoft;

http://www.tsoftonline.com