Pile Buck (SPW911) - Terzaghi Pressure Model

[justhumm]

I'm playing with a sheet pile wall design (in Pile Buck SPW911 ver. 2.0, with tie backs) in a mostly soft clay soil; and (as per the software's error message) am analyzing it using the Terzaghi Pressure Model (which I assume is based on Log-Spiral theory).

I am interested in finding some more background and theoretical information on the variables used in that model (specifically, m = 0.4 or 1.0 and a = 0.2 - 0.4), because when I change one of them, I am getting wild variations in the results.

There is a little bit of information in the old pile buck design manual (1987, pg. 22 and 119), though I am not gaining a lot from it.

If anyone can shed some light on the Terzaghi variables (m and a, as used in Pile Buck / SPW911), or if anyone can suggest a good reference for them, I would appreciate it.

Thanks.

 

[vulcanhammer]

It's been a while since I've dealt with SPW 911, but let me shed some light on a point or two.

First: "Terzaghi" earth pressure has nothing to do with log-spiral slip surfaces. It refers to the Terzaghi & Peck trapezoidal earth pressure distribution traditionally associated with braced excavations. The only other options in SPW 911 are Rankine and Coulomb earth pressure theories.

Some information on the m and a variables can be found at the "Terzaghi & Braced Cofferdams FAQs" page

http://pilebuck.com/spw911support05.html

You said you're using 2.0. I'd try to obtain a higher version; some of the features were expanded and, of course, some user-spotted difficulties were addressed. Also, Pile Buck's replacement for the PBSSPDM is Sheet Pile Design by Pile Buck, which can be found at

http://www.lulu.com/content/paperback-book/sheet-pile-design-by-pile-buck/1237619

It includes some worked examples using SPW 911.

It's also worth noting that most of the theory in SPW 911 was taken from the BSC/Ciria books on the subject.

http://www.pz27.net