The soil spring constants need to obtain by conducting plate load test results ..from the test results spring constant (subgrade modulus) can be obtained..lot of literature available on this topic..so you can collect literature and calculate modulus based on literature ..

There are many empirical formulas that relate the soil reaction module (ballast coefficient) with different mechanical properties of the soil, mainly with the deformation module and with the Poisson module. There is a lot of information in that network

There are many correlation works between the properties of the soil and the reaction module, entering the internet with that title you can find many, I just give you some examples of related articles

1. IAEG2006 Paper number 505© The Geological Society of London 20061Evaluation of modulus of subgrade reaction (Ks) in gravely soils basedon SPT resultsREZA ZIAIE MOAYED1 & SEYED ABOLHASSAN NAEINI

2.

Correlation between Subgrade Reaction Modulus and CBR for Airport Pavement Subgrades

📷 Kairat Tuleubekov 📷 David Brill

3.

Correlation between Soil Bearing Capacity and Modulus of Subgrade Reaction

Dec, 2013 By Apurba Tribedi In Articles, Structural Design Comments 44

4. Evaluation of Modulus of Elasticity and Modulus of Subgrade Reaction of Soils Using CBR Test

• January 2012
• DOI:
• 10.5923/j.jce.20120201.05
• 📷Elsa Putri
• N. S. V Kameswara Rao
• 📷Md. Abdul Mannan
• I hope the information can be useful regards Dr. Sc. Gilberto Quevedo