# shape factors



## Road Guy (Aug 22, 2006)

I have noticed by doing some different geotech problems that the CERM shape factors are much different than using the forumulas (provided in basically every other geotech book than the CERM)

anyone have a clue on which is "more correct" or current?


----------



## cement (Aug 24, 2006)

dang I'm glad I passed

It makes me wonder how ML got to be an expert at everything. you can study empiricle science like soils all your life and still have stuff to learn. does the six minute solutions geotech book ask those questions?


----------



## Road Guy (Aug 25, 2006)

the 6 minute is "close" to the Cerm, but they even use a lot of forumulas for the solutions that are not in the Cerm, even the AM questions.

I was doing some problems out of some GLP Books, fairly decent, but I think the CERM says a shape factor for a square fotting is always 0.85, when you use the shape factor formula it actually comes out to a 0.6.

I dont have the formula in front of me, but I have noticed most other books (outside the PPI group) all seam to use the shape factor formula versus the tables in the CERM??


----------



## RIP - VTEnviro (Aug 25, 2006)

> you can study empiricle science like soils all your life and still have stuff to learn. does the six minute solutions geotech book ask those questions?


That and soils are such a subjective thing. You can have 10 different engineers look at a test pit or sample and come up with 10 different analyses.

Is it sandy silt or silty sand? :dunno:


----------



## cement (Aug 25, 2006)

> I dont have the formula in front of me, but I have noticed most other books (outside the "the other board" group) all seam to use the shape factor formula versus the tables in the CERM??


I always liked to use a clean formula rather than plotting on a graph, but that is a personal choice. I think about a bunch of grad students pounding samples and collection a bunch of points, then ramming them into a formula. It seems more precise than drawing a net and fitting a rectangle or a square over it.


----------



## EL Nica PE (Aug 29, 2006)

As a Geotechnical practicing engineer, we always use tables values.

Only phds people go with the formulas...


----------

