Sensitivity Analysis of Flexible Pavement Response and AASHTO 2002 Design Guide for Properties of Unbound Layers

Sensitivity Analysis of Flexible Pavement Response and AASHTO 2002 Design Guide for Properties of Unbound Layers
Author: Sanaa Masad
Publisher:
Total Pages:
Release: 2004
Genre: Aggregates (Building materials)
ISBN:

Unbound granular materials are generally used in road pavements as base and subbase layers. The granular materials provide load distribution through aggregate contacts to a level that can help the subgrade to withstand the applied loads. Several research studies have shown that unbound pavement layers exhibit anisotropic properties. Anisotropy is caused by the preferred orientation of aggregates and compaction forces. The result is unbound pavement layers that have higher stiffness in the vertical direction than in the horizontal direction. This behavior is not accounted for in the design and analysis procedures included in the proposed AASHTO 2002 design guide. One of the objectives of this study is to conduct a comparative analysis of flexible pavement response using different models for unbound pavement layers: linear isotropic, nonlinear isotropic, linear anisotropic and nonlinear anisotropic. Pavement response is computed using a finite element program. The computations from nonlinear isotropic and anisotropic models of unbound layers are compared to the AASHO field experimental measurements. The second objective is to analyze the influence of using isotropic and anisotropic properties for the pavement layers on the performance of flexible pavements calculated using the AASHTO 2002 models. Finally, a comprehensive sensitivity analysis of the proposed AASHTO 2002 performance models to the properties of the unbound pavement layers is conducted. The sensitivity analysis includes different types of base materials, base layer thicknesses, hot mix asphalt type and thickness, environmental conditions, and subgrade materials.

ANALYSIS OF FLEXIBLE PAVEMENTS INCORPORATING NONLINEAR RESILIENT BEHAVIOR OF UNBOUND GRANULAR LAYERS.

ANALYSIS OF FLEXIBLE PAVEMENTS INCORPORATING NONLINEAR RESILIENT BEHAVIOR OF UNBOUND GRANULAR LAYERS.
Author:
Publisher:
Total Pages:
Release: 2004
Genre:
ISBN:

Traditionally, the resilient modulus values obtained from repeated unconfined or triaxial compression tests are used as the elastic modulus of granular layers in structural analysis of flexible pavements. Sometimes the resilient modulus of granular materials are estimated from known California bearing ratios (CBR) or stabilometer resistance (R) values by simple regression equations. On the other hand, it is well known that stress-strain relation for unbound granular materials is nonlinear and the resilient modulus increases with the increase in stress intensity. There exist several models for stress dependent nonlinear behavior of unbound granular materials. These models are incorporated into elastic layered analysis by applying a method of successive approximations in order to get more realistic pavement responses. Kenlayer is a popular computer program incorporating nonlinear behavior of granular materials in elastic layered system. In this computer program, the resilient modulus of granular materials are varied in vertical direction only, without considering variations in radial direction. In this study, simplest model namely K-Q model for stress dependency of granular layer is applied in structural analysis of flexible pavements. This model is adopted for use in finite element analysis carried by SAP90 software. Analyses are performed over 24 different three-layered pavement structures by changing asphaltic concrete modulus values, granular base thicknesses, base materials and subgrade modulus values. Critical pavement responses namely tensile strains at the bottom of asphaltic surface layers and compressive strains on top of subgrade are obtained for each pavement by linear layered elastic, nonlinear layered elastic and nonlinear finite element solutions. The pavement lives are calculated by using selected performance equations. The results of layered systems and finite element solutions are compared. It is observed that, results obtained from finite element mo.

Pavements Unbound

Pavements Unbound
Author: Andrew Dawson
Publisher: CRC Press
Total Pages: 388
Release: 2014-09-01
Genre: Technology & Engineering
ISBN: 9781439833803

Nearly all highway, airport, dock and industrial pavements contain large quantities of untreated aggregate in the form of unbound pavement layers. In many pavements, which are lightly or moderately trafficked, crushed rock or gravel derived aggregates comprise the majority of the construction or, in the case of unsealed pavements, all of the structure. This book provides studies of the performance and description of this material that will help the reader to better understand its characteristics and behaviour both alone and as part of the pavement structure it forms. This work will be useful to practitioners, policy makers, researchers and students. It forms a sequel to the earlier book "Unbound Aggregates in Road Construction" also published by Balkema

Practices for Unbound Aggregate Pavement Layers

Practices for Unbound Aggregate Pavement Layers
Author: E. Tutumluer
Publisher:
Total Pages: 180
Release: 2013
Genre: Aggregates (Building materials)
ISBN:

"TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 445: Practices for Unbound Aggregate Pavement Layers consolidates information on the state-of-the-art and state-of-the-practice of designing and constructing unbound aggregate pavement layers. The report summarizes effective practices related to material selection, design, and construction of unbound aggregate layers to potentially improve pavement performance and longevity."--Publisher website.