What is N'value and how N'value decides the type of foundation

Hi friends, I need know some thing in Soil mechanics / Soil report

What is N'value and how N'value decides the type of foundation such as shallow or deep of the building? Any value limits or thumb rule is there.... Please make me clarified.

Thanks in advance!

Regards,
K. Prakash
 
The borehole is drilled deeper and the test is repeated. Often soil recovery is poor and counting errors per interval may occur. The number of hammer strikes it takes for the tube to penetrate the second and third 6 inch depth is called the 'standard penetration resistance', or otherwise called the 'N-value'