SPT and CPT tests

[scottiesei]

I am in desperate need of a variety of N-value and qc correlations for SPT and CPT tests. I am looking to determine values such as Cu, OCR, Dr and Phi. Please help!

 

[Guest]

I am in desperate need of a variety of N-value and qc correlations for SPT and CPT tests. I am looking to determine values such as Cu, OCR, Dr and Phi. Please help!

Scottie --

Do you have a copy of Fundamentals of Geotechnical Engineering, Braja M. Das ?? Chapter 8 - Subsurface Exploration has some emperical relationships for blow counts, strengths, etc.

I am cautiously mentioning this because I see information relative to qu - not qc.

I also have Soil Mechanics in Engineering Practice, 3rd Ed by Terzaghi, Peck, and Mesri -- I haven't had a chance to go through it yet.

I will update when I get a little time.

JR

 

[scottiesei]

JR-

I have neither book. I have some Das books, but they do not have what I need. I am working on the project this evening so any eqs u can throw my way would be appreciated.

Thanks!

 

[Guest]

JR-I have neither book. I have some Das books, but they do not have what I need. I am working on the project this evening so any eqs u can throw my way would be appreciated.

Thanks!

A few quickies that I have come across:

Cu (kN/m2) = 29*N0.72 - Hara, et al. (1971)

OCR = 0.1938(N/eff vert stress)0.689 - Mayne and Kemper (1988)

---> eff vert stress in units of MN/m2

Ncor = CN*NF

Such that values for CN obtained by:

Liao and Whitman (1986): 9.78*SQRT(1/eff overburden pressure)

Skempton (1986): 2/(1+0.01*(eff overburden pressure))

Peck (1974): 0.77*log(1912/eff overburden pressure) for eff overburden pressure > 25 kN/m2

Soil Friction Angle Relationships

phi = 27.1 + 0.3Ncor - 0.00054(Ncor)2 Wolff (1989)

phi = SQRT(20*Ncor) + 20 Hantanaka and Uchida (1996) *** NOTE - I have seen this used frequently ***

JR

 

[Geotech.PE]

Japanese Geotechnical Society modified the phi = SQRT(15*Ncor) + 15 to new equation in 1996. Japanese use this equation regularly in their design. Japan has EQ more than anywhere in the world (if you live in Tokyo area, you can feel EQ almost once every week). The equation is very simple, and well recognized. If it works in EQ active country like Japan, why not in US and rest of the world.

phi = SQRT(20*Ncor) + 20 Hantanaka and Uchida (1996) *** NOTE - I have seen this used frequently ***

Well, regarding the geotechnical main text books, I studied BM Das's book as main textbook during my Masters Studies for foundation engineering part, but I recently found a new book by Muni Budhu of Univ of Arizona, published by JWS. BM Das's book have several titles that make his books too confusing as a reference material for Exam preparations. BM Das's book lists too many equations, and he drops out Most of these equations in subsequent edition, and replace by new equations. I feel that BM Das just tries to justify frequent new edition by adding and dropping out these large number of equations. If you can not last these equations for just two editions, why should you list these equations if it is not just to confuse readers, and validate a new edition every alternate year.

As I went through Muni Budhu's new book, I find the book having only the most frequently used equations, which makes me very comfortable. I would have appreciated Muni Budhu more if he has just made several tables of equations from current research papers, without adding them in / clogging the main text part, so that it also helps those who want these new developments as well.

IMO, Muni Budhu's book will replace BM Das's book(s) on foundation and geotechnical engineering. Muni Budhu has two books one of them is currently in second edition (good for Geotechnical Engineering I course) and the other one is in first edition (good for Geotechnical Engineering II course). Should I need to take the PE Exam in future, I will buy Muni Budhu's book instead of BM Das's several booooooooooooooooooks so that I can save my time, effort, and avoid confusions which book and which edition to use. I hope I will not be fired by BMDas or his publisher. I apologize if I sound like a cynical guy.

A GeoCivil Guy "PoGy"

 

[Guest]

IMO, Muni Budhu's book will replace BM Das's book(s) on foundation and geotechnical engineering. Muni Budhu has two books one of them is currently in second edition (good for Geotechnical Engineering I course) and the other one is in first edition (good for Geotechnical Engineering II course). Should I need to take the PE Exam in future, I will buy Muni Budhu's book instead of BM Das's several booooooooooooooooooks so that I can save my time, effort, and avoid confusions which book and which edition to use. I hope I will not be fired by BMDas or his publisher. I apologize if I sound like a cynical guy.

Thanks for the heads up on the text!

I have completed my MS with focus in Geotechnical Engineering as well. While I find that the Das texts are probably more complete (subject wise) than other geotechnical engineering texts I agree that many of the equations don't have proper attribution or sufficient explanations for when they are applicable. On many occasions, I have been forced to chase down explanations for numerous equations presented in his books.

No problem with presenting a dissenting opinion on the Das texts - you are just offering an honest opinion. I have done the same with other texts as well ...

Regards,

JR