Resilient behavior of compacted subgrade soils under the repeated triaxial test

Daehyeon Kim, Jong Ryeol Kim

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


Subgrade soils are very important materials to support highways. Resilient modulus (Mr) has been used for characterizing stress-strain behavior of subgrades subjected to repeated traffic loadings. Recently the repeated triaxial test procedure has been upgraded through AASHTO T 307. Since the testing procedure is still complex, the testing has not been widely implemented in practice. In order to evaluate resilient behavior of compacted subgrades soils, the repeated triaxial test and the unconfined compressive test as well as some fundamental property tests were conducted. In this study, the applicability of a simplified procedure with a confining pressure of 13.8 kPa and deviator stresses of 13.8, 27.6, 41.4, 55.2, 69 and 103.4 kPa was investigated on the typical sandy-silty-clay and silty-clay subgrade soils encountered in Indiana. The results obtained from the simplified procedure are comparable with those obtained from AASHTO T 307 which calls for 15 combinations of stresses. This shows the simplified procedure to be feasible and effective for design purpose. Some soils compacted wet of optimum moisture content showed an excessive permanent deformation. This phenomenon was investigated by the comparison of the unconfined compressive test and the repeated triaxial test results. For soils exhibiting excessive permanent deformation, use of deformed length is desirable for more accurate calculation of Mr. Usually the soils compacted dry of optimum shows the largest Mr for sandy-silty-clay soils due to capillary suction, but it is not necessarily true for silty-clay soils. A predictive model to estimate regression coefficients k1, k2, and k3 using 11 soil variables obtained from the soil property tests and the standard Proctor compaction tests was developed. The predicted regression coefficients compare well with measured ones.

Original languageEnglish
Pages (from-to)1470-1479
Number of pages10
JournalConstruction and Building Materials
Issue number7
Publication statusPublished - Jul 1 2007


  • Permanent deformation
  • Predictive model
  • Regression coefficients
  • Resilient modulus
  • Silty-clay soils
  • Soil properties

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Materials Science(all)

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