SPT N value~

[Chunil]

Hello~
I am first here to post something~
My question is as follows~

Is there any way to convert 50 blows per 30cm into N blows per 30cm ?

For example, 50/15 means 50 blows were needed to penetrate 15cm.
What I want is that in the case of blow count which exceeds 30 blows like above example..how can I convert it to blow count needed to penetrate 30cm...

50/15 ---> ?blows/30cm
50/1 ---> ?blows/30cm

Sometimes it is needed to and wish to convert them to N-blow count per 30 cm....

Pleasre let me know the way to convert(if exists) and reference which concerns about it~

Thank u

 

[Ron]

There is a practical upper limit of the "N" value, where anything greater than the upper limit is irrelevant to the parameters dependent upon the "N" value.

For your case, 50 blows for 1cm would represent an extremely dense or hard material and you might be better served to attempt coring that material if you actually needed some material properties.

You have to be careful when you try to extrapolate "N" values beyond actual measurements. For example, a 15cm sample length might not actually represent the conditions that would affect the structure, as it might be a lense of soil with different properties.

 

[tstatnall]

I'm looking for a formula and references that can be used to convert California (2.5"ID/3.0"OD?) and Modified California split-spoon (2.0"ID/2.5"OD) sample blow count to N-values.

 

Is there any information on railway formation design built over swampland CBR value less than 3. Formation floating on a raft of spent ballast- flexible and pumping formation.