Japanese Standard blowcount Nj 1

[eureka]

In the ASCE Technical Engineering and Design Guide SETTLEMENT ANALYSIS (US Army Corps of Engineers, No 9), Chapter 4, Table 4-1, there is a reference to Nj which is the blowcount by Japanese standards. How do this differ from the normal blowcount N from the Standard Penetration Test?

 

[harney]

The "blowcount by Japanese Standards" may refer to the variation of energy input in the SPT test. This depends on many factors, like hammer release system type, hammer type, anvil, etc etc. N-values are typically corrected to a common energy level of 60% (ratio of the imparted energy to the theoretical free-fall potential energy).

So: N(60) = N*(ER / 60)

Japanese systems are typ much more efficient than 60% (close to 80%). However, I'm unsure whether applying this energy correction will lead to the "blowcount by Japanese Standards."

 

[BigH]

Look up the Reference given at the end of the manual. I don't have it here but the manual is likely well documented.

 

[TLSC]

Hey why waste your time with these guys.

Here it is.

Nj = 0.833(N1)60

The paper that mentions the Japanese hammer came from the following paper:

Ishihara, 1993. Liquefaction and Flow Failure During Earthquakes, Geotechnique, Vol. 43, No. 3, pp. 351-415.

 

[BigH]

True Eureka - you can wait 3 1/2 months for TLSC. Don't forget, you have to now figure (N1).

 

[TLSC]

I just joined this forum about 2 days ago, so excuse me for posting this 3.5 months late.

 

[BigH]

Suggest, then, you keep the sarcasm down until you know the various participants.
and welcome to the site!