A Framework to Utilize Shear Strength Properties for Evaluating Rutting Potentials of Unbound Aggregate Materials

Issam Qamhia, Erol Tutumluer, Liang Chern Chow, Debakanta Mishra

Research output: Contribution to journalConference articlepeer-review


This paper presents shear strength and permanent deformation trends of four unbound aggregate materials, commonly used for base and subbase layers in the state of North Carolina, USA, studied through repeated load triaxial testing, using the University of Illinois FastCell equipment. A testing and modeling framework has been established to develop a proper permanent deformation prediction model, referred to herein as the UIUC rutting model, with number of load applications. According to the framework, the unbound aggregate shear strength properties are incorporated into the model using the ratio of the applied wheel load shear stress to the mobilized shear strength, i.e., the Shear Stress Ratio (SSR). This requires conducting repeated load permanent deformation tests at SSR values of 0.25, 0.5 and 0.75 to determine the trends in permanent deformation accumulation. The prediction ability of the developed UIUC rutting model is evaluated in this paper for the four materials tested at both an engineered target gradation and source gradations.

Original languageEnglish (US)
Pages (from-to)911-920
Number of pages10
JournalProcedia Engineering
StatePublished - 2016
Event3rd International Conference on Transportation Geotechnics, ICTG 2016 - Guimaraes, Portugal
Duration: Sep 4 2016Sep 7 2016


  • Aggregate Gradation
  • Aggregate Rutting Model
  • Permanent Deformation
  • Repeated Load Triaxial Testing
  • Shear Stress Ratio
  • Triaxial Shear Strength Testing
  • Unbound Aggregate Testing

ASJC Scopus subject areas

  • General Engineering

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