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  • VTT P

    UB

    LICA

    TION

    S 702 Calculation m

    ethod for permanent deform

    ation of unbound pavement...

    Korkiala-Tanttu

    ESPOO 2008ESPOO 2008ESPOO 2008ESPOO 2008ESPOO 2008 VTT PUBLICATIONS 702

    Leena Korkiala-Tanttu

    Calculation method for permanentdeformation of unbound pavementmaterials

    An analytical-mechanistic method for the calculation of permanentdeformations in unbound pavement layers and subgrade has beendeveloped at VTT. The calculation method is needed in the analyticaldesign procedure of pavements. The calculation method was generatedbased on the test results of accelerated pavement tests along with thecomplementary laboratory tests made in Finland.

    The developed calculation method for unbound materials was basedon an analytical, nonlinear elasto-plastic model. The stress state of thestructure was modelled using finite element method and non-linearelasto-plastic material model. The deformations were then calculated foreach layer from the number of passes, the bearing capacity of thematerial and its stress state. The saturation and compaction degrees weretaken into account by varying material parameters. So far only the basicmaterial parameters are known, thus more material studies are needed.

    The method was tested against two Finnish accelerated pavementtests. The results indicated that the material model gave tolerable resultsfor the high load levels. For the lower load levels the method gave morereliable results. The method can also be applied to the comparison of thesensitivity of different structures against rutting.

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    ISBN 978-951-38-7135-2 (soft back ed.) ISBN 978-951-38-7136-9 (URL: http://www.vtt.fi/publications/index.jsp)ISSN 1235-0621 (soft back ed.) ISSN 1455-0849 (URL: http://www.vtt.fi/publications/index.jsp)

    Julkaisu on saatavana Publikationen distribueras av This publication is available from

    VTT VTT VTTPL 1000 PB 1000 P.O. Box 1000

    02044 VTT 02044 VTT FI-02044 VTT, FinlandPuh. 020 722 4520 Tel. 020 722 4520 Phone internat. + 358 20 722 4520

    http://www.vtt.fi http://www.vtt.fi http://www.vtt.fi

  • VTT PUBLICATIONS 702

    Calculation method for permanent deformation of unbound

    pavement materials

    Leena Korkiala-Tanttu

    Dissertation for the degree of Doctor of Science in Technology (Doctor of Philosophy) to be presented with due permission of the Department of Civil and Environmental Engineering, Helsinki University of Technology for public

    examination and debate in Auditorium M1 at Helsinki University of Technology (Espoo, Finland) on the 30th of January, 2009, at 12 noon.

  • ISBN 978-951-38-7135-2 (soft back ed.) ISSN 1235-0621 (soft back ed.)

    ISBN 978-951-38-7136-9 (URL: http://www.vtt.fi/publications/index.jsp) ISSN 1455-0849 (URL: http://www.vtt.fi/publications/index.jsp)

    Copyright VTT 2008

    JULKAISIJA UTGIVARE PUBLISHER

    VTT, Vuorimiehentie 5, PL 1000, 02044 VTT puh. vaihde 020 722 111, faksi 020 722 7001

    VTT, Bergsmansvgen 5, PB 1000, 02044 VTT tel. vxel 020 722 111, fax 020 722 7001

    VTT Technical Research Centre of Finland, Vuorimiehentie 5, P.O. Box 1000, FI-02044 VTT, Finland phone internat. +358 20 722 111, fax +358 20 722 7001

    Technical editing Maini Manninen Edita Prima Oy, Helsinki 2008

    http://www.vtt.fi/publications/index.jsphttp://www.vtt.fi/publications/index.jsp

  • 3

    Korkiala-Tanttu, Leena. Calculation method for permanent deformation of unbound pavement materials [Tierakenteen sitomattomien materiaalien pysyvien muodonmuutosten laskentamenetelm]. Espoo 2008. VTT Publications 702. 92 p. + app. 84 p.

    Keywords permanent deformations, rutting, unbound pavement material, pavement design,stress distribution

    Abstract

    An analytical-mechanistic method for the calculation of permanent deformations of pavements has been developed at the Technical Research Centre of Finland (VTT) over some years by the author. The calculation method is needed in the analytical design procedure of pavements. This research concentrated on the calculation method for permanent deformations in unbound pavement materials. The calculation method was generated based on the results of full-scale accelerated pavement tests along with the complementary laboratory tests together with finite element calculations.

    The objective was to develop a relatively simple material model for unbound materials, which is an analytical, nonlinear elasto-plastic model. The stress distribution studies of traffic load showed that it is very important to calculate stresses in pavements with an elasto-plastic material model to avoid false tensile stresses in unbound materials, especially when the asphalt layers are thin.

    The new material deformation model can take into account the amount of the loading, the number of vehicle or wheel passes, the deformation capacity of the material and its stress state. The strains in each layer and subgrade are calculated and converted to the vertical deformations and then summed to obtain the total rutting. The method was verified against two Finnish accelerated pavement tests. The results indicated that the material model gave tolerable results for the relativel

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