Estimation of Subgrade Resilient Modulus for Fine-Grained Soil from Unconfined Compression Test

Abstract

The resilient modulus of subgrade soil is used to design a pavement structure that is adequate for the expected traffic and environmental loading. Both mechanistic and empirical design procedures use this property. The resilient modulus test is a complex test that requires significant resources, including a high level of technical ability on the part of the operator. For smaller or less critical projects with a low volume of traffic where costly and complex resilient modulus testing is not justified, a correlation with other, simpler tests could be used. In this study, a correlation with the results of an unconfined compression (UC) test is explored for estimation of the resilient modulus of fine-grained soils. This paper presents several models with which to estimate the resilient modulus of fine-grained soil from the results of UC tests considering two sample preparation techniques: static and impact compaction. The simplest model considers only unconfined compressive strength to predict the resilient modulus with a fair correlation. The more detailed models also consider the plasticity index, percentage of material passing the Number 200 sieve, and modulus of the stress–strain curve from the UC test. The sample preparation technique had a significant influence on the UC test results.