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Title:Permanent deformation behavior of unbound granular materials and rutting model development
Author(s):Chow, Liang Chern
Advisor(s):Tutumluer, Erol
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Unbound granular material
Permanent deformation
Shear strength
Shear Stress Ratio
Repeated load triaxial testing
Mechanistic-Empirical Pavement Design Guide (MEPDG)
Rutting model
Abstract:The rutting damage model as incorporated into the AASHTO’s mechanistic-empirical (M-E) pavement design approaches (i.e. Pavement ME Design) was found to produce inadequate rut estimates in unbound aggregate base/subbase layers by discounting the contribution of stress state from the original Tseng and Lytton (1989) model. This research study was aimed at developing a new permanent deformation prediction model that would properly take into account the effects of applied load, applied stress in relation to material’s strength and number of load cycles through a well-established laboratory test matrix for mechanical properties. Sixteen (16) different unbound granular materials commonly used in the state of North Carolina (NC) for pavement subbase/base applications were used in this study. The goal was to accurately estimate the field performances of aggregate base courses through development of a new rutting damage model, referred to as UIUC rutting model. The laboratory phase of this study presented in this thesis considered a target engineered gradation within the lower and upper limits of North Carolina Department of Transportation (NCDOT) base course specification bands with established moisture-density relationship for each of the selected granular materials. Experimental characterizations primarily consisted of imaging based aggregate shape analyses, moisture-density, resilient modulus, shear strength, and permanent deformation tests based on a comprehensive test matrix. The concept of Shear Stress Ratio (SSR) or stress/strength level, which can be derived from Mohr-Coulomb failure criteria, was introduced in this study to properly examine the effects of varying degree of stress/strength to permanent deformation behavior of unbound materials. These test results established a complete database to develop the UIUC rutting model in order to properly capture the effects of stress state and material properties. The model predictions were compared with Pavement ME Design results to justify the validity and performance of the proposed model.
Issue Date:2014-09-16
Rights Information:Copyright 2014 Liang Chern Chow
Date Available in IDEALS:2014-09-16
Date Deposited:2014-08

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