Krey method

[MHobbs]

https://www.eng-tips.com/viewthread.cfm?qid=427296

I was very interested in this thread. I made this simple calculator have I correctly interpreted the Krey method?
I have set it up for using with PCC concrete so a friction angle of 15.

 

[SlideRuleEra]

have I correctly interpreted the Krey method?

I get L = 1.000 m for these conditions, not 1.0776.

 

[MHobbs]

Is that not the value for L'

 

[SlideRuleEra]

Oh, yes... that is what it says (in words)...

but, from time to time the math says something else:

My choosing δ = 15^o is not just some "random" slope. Fifteen degrees is a good practical slope, about 3.7 horizontal : 1 vertical, but I picked that value, δ = ρ, to easily "stress-test" the math in the spreadsheet... and the spread sheet "flunked", it is spitting out garbage.

The Krey paper (which I posted on the referenced thread) also say:

which is:

and if that is not enough, I solved the problem the old-fashion way... analog, scaled drawing using pencil & paper, following Krey's (Figure 102) instructions:

When you start at h/3, draw a line angled "down" 15^o, measure off h/10, then draw a line angled "up" 15^o... surprise... you are right back where you started... L = 1.00 m.

As a matter of fact, if you choose the "right" value, say δ = 20^o... L < 1.00m.