MRSG Calc

The Resilient Modulus is a basic subgrade soil stiffness/strength characterization commonly used in structural design of pavements. Resilient Modulus is a measure of the elastic response of a soil (e.g., how well a soil is able to return to its original shape and size after being stressed) under repeated loading. This app, based on the conversion factors included in NCHRP Report 128, “Evaluation of AASHTO Interim Guide for the Design of Pavement Structures,” allows you to quickly estimate the Subgrade Resilient Modulus (MRSG) from either a California Bearing Ration (CBR) or Resistance Value (R-value) measurement and then see a subgrade k-value corresponding to your MRSG. The conversion from resilient modulus of the subgrade to k-value was updated in the fall of 2011 to better reflect published test results; the constant conversion factor of 19.4 as suggested in the AASHTO Guide for Design of Pavement Structures 1993 is no longer used.