Predicting Subgrade Resilient Modulus for Use in the MEPDG Using Common Soil Indices
In roadway pavement design, one must consider the performance of the pavement structure and mixture design. The tendency for pavement to be more flexible in nature gives increased importance to the properties and condition of the underlying soil subgrade. Traditional foundation design normally considers the static strength response of the soil from stationary loads. Roadway pavement design, however, must consider the dynamic strength response created by moving traffic loads. This dynamic strength of soil, or “stiffness,” is known as its resilient modulus (MR). The resilient modulus is determined by costly and time-consuming laboratory tests. For these reasons, it would be greatly beneficial to find an effective, yet simpler method to determine the values of MR. The goal of this study was to utilize multiple regression analyses to determine the relationships between common soil index properties, MR, and use these relationships to create an equation to model. The methodology used in the creation of these equations will be described as well as a statistical evaluation of their performance. Subgrade soil property data for 253 different soils found in northeast Texas was mined from Arizona State University’s “National Catalog of Natural Subgrade Properties Needed for the ME-PDG Input.” The common soil index properties studied include five sieve analysis gradations, liquid limit, and plasticity index. These properties were analyzed against MR.
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