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Performance model for unbound grnular materials pavements
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Recently, there has been growing interest on the behaviour of unbound granular material in road base layers. Researchers have studied that the design of a new pavement and prediction of service life need proper characterization of unbound granular materials, which is one of the requirements for a new mechanistic design method in flexible pavement.

Adequate knowledge of the strength and deformation characteristics of unbound layer in pavements is a prerequisite for proper thickness design, residual life determination, and overall economic optimization of the pavement structure. The current knowledge concerning the granular materials employed in pavement structures is limited. In addition, to date, no general framework has been established to explain satisfactorily the behaviour of unbound granular materials under the complex repeated loading which they experience.

In this study, a conceptual method, packing theory-based model is introduced; this framework evaluates the stability and performance of granular materials based on their packing arrangement. In the framework two basic aggregate structures named as Primary Structure (PS), and Secondary Structure (SS). The Primary Structure (PS) is a range of interactive grain sizes that forms the network of unbound granular materials. The Secondary Structure (SS) includes granular materials smaller than the primary structure. The Secondary Structures fill the gaps between the particles in the Primary Structure and larger particles essentially float in the skeleton.

In this particular packing theory-based model; the Primary Structure porosity, the average contact points (coordination number) of Primary Structure, and a new parameter named Disruption Potential are the key parameters that determine whether or not a particular gradation results in a suitable aggregate structure.

Parameters mentioned above play major role in the aggregate skeleton to perform well in terms of resistance to permanent deformation as well as load carrying capacity (resilient modulus). The skeleton of the materials must be composed of both coarse enough and a limited amount of fine granular materials to effectively resist deformation and carry traffic loads.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , xiii, 18 p.
Series
Trita-TSC-LIC, 12-004
Keyword [en]
unbound granular materials, aggregate, packing theory, gradation, primary structure, secundary structure, permanent deformation, resilient modulus
National Category
Civil Engineering
Identifiers
URN: urn:nbn:se:kth:diva-97752ISBN: 978-91-85539-89-5 (print)OAI: oai:DiVA.org:kth-97752DiVA: diva2:533658
Presentation
2012-06-01, B26, KTH, Brinellvägen 23, Stockholm, 09:00 (English)
Opponent
Supervisors
Note
QC 20120601Available from: 2012-06-14 Created: 2012-06-14Bibliographically approved
List of papers
1. Packing theory-based framework to evaluate permanent deformation of unbound granular materials
Open this publication in new window or tab >>Packing theory-based framework to evaluate permanent deformation of unbound granular materials
2013 (English)In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 14, no 3, 309-320 p.Article in journal (Refereed) Published
Abstract [en]

Permanent deformation of unbound granular materials plays an essential role in the long-term performance of a pavement structure. Stability of unbound granular materials is defined by the particle-to-particle contact of the system, the particle size distribution and the packing arrangement. This paper presents a gradation model based on packing theory to evaluate permanent deformation of unbound granular materials. The framework was evaluated by using 10 unbound granular materials from different countries. The disruption potential, which determines the ability of secondary structure (SS) to disrupt the primary structure (PS), is introduced. This study also identified the amount of PS and SS that may eventually be used as a design parameter for permanent deformation of unbound road layers. The evaluation of the model regarding permanent deformation behaviour of granular materials is found to compare favourably with experimental results.

Place, publisher, year, edition, pages
Taylor & Francis, 2013
Keyword
gradation, unbound materials, packing theory, primary structure, secondary structure, disruption potential, permanent deformation
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-97750 (URN)10.1080/10298436.2012.736620 (DOI)000322305800008 ()2-s2.0-84873576997 (Scopus ID)
Note

QC 20150625. Updated from submitted to published.

Available from: 2012-06-14 Created: 2012-06-14 Last updated: 2017-12-07Bibliographically approved
2. Packing theory-based framework for evaluating resilient modulus of unbound granular materials
Open this publication in new window or tab >>Packing theory-based framework for evaluating resilient modulus of unbound granular materials
2014 (English)In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 15, no 8, 689-697 p.Article in journal (Refereed) Published
Abstract [en]

Enhancing the quality of granular layers is fundamental to optimise the structural performance of the pavements. The objective of this study is to investigate whether previously developed packing theory-based aggregate parameters can evaluate the resilient modulus of unbound granular materials. In this study, 19 differently graded unbound granular materials from two countries (USA and Sweden) were evaluated. This study validated both porosity of primary structure (PS) and contact points per particle (coordination number) as key parameters for evaluating the resilient modulus of unbound granular materials. This study showed that decreasing the PS porosity - higher coordination number - calculated based on the proposed gradation model, yields higher resilient modulus. Good correlation was observed between the proposed packing parameters and resilient modulus of several types of aggregates. The packing theory-based framework successfully recognised granular materials that exhibited poor performance in terms of resilient modulus.

Place, publisher, year, edition, pages
Taylor & Francis, 2014
Keyword
unbound materials, packing theory, primary structure, porosity, coordination number, and resilient modulus
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-97751 (URN)10.1080/10298436.2013.857772 (DOI)000334073500002 ()2-s2.0-84897914058 (Scopus ID)
Note

QC 20140520

Available from: 2012-06-14 Created: 2012-06-14 Last updated: 2017-12-07Bibliographically approved

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