Vertical Modulus of Subgrade Reaction

http://www.bing.com/search?q=vertical+modulus+of+Subgrade+Reaction&src=IE-Address

For gravely and sandy soils (non-cohesive soils), one popular test method is to utilize the Plate Load Test (PLT), as defined under ASTM D1194 Standard.

Another testing method is the Standard Penetration Test (SPT).

You should really do a Google Search for "USACE Engineering Manuals" (EM), and totally familiarize yourself with soils engineering and relevant testing standards using the appropriate EM manual.

Apparently, since you are asking this basic question, it appears to me that you haven't received any formal soils engineering and material testing....