Effects of Unbound Layer Cross-Anisotropy on Pavement Responses

The effects of cross-anisotropy of unbound layer materials on the stress-strain response of a pavement under Falling Weight Deflectometer (FWD) test load are determined at three temperatures employing a dynamic Finite Element Model (FEM) in ABAQUS. Viscoelastic behavior of asphalt materials are characterized by Prony series coefficients estimated from laboratory dynamic modulus test. Nonlinear elastic behavior of base material is incorporated in ABAQUS through a User Defined Material (UMAT) subroutine. Subbase and subgrade materials are modeled as linear elastic material using the FWD backcalculated moduli and Poisson's ratio. Cross-anisotropy is introduced in the FEM model by changing the ratio of horizontal to vertical stiffness (n-value) of unbound layers, namely base, subbase, and subgrade layers of an instrumented pavement. FEM model is validated using field collected stress-strain responses under FWD loading from the instrumented pavement section at mile post 141 (MP 141) on Interstate 40 (I-40) near Albuquerque, New Mexico. It is observed that the tensile strain at the bottom of the Asphalt Concrete (AC) layer is significantly influenced by the base layer cross-anisotropy. The vertical strain in the AC layer is barely affected by the cross-anisotropy of the unbound layers. However, vertical strains in the unbound layers are significantly affected by cross-anisotropy. Therefore, it can be postulated that fatigue damage that is caused by tensile strain at the bottom of AC layer, and unbound layer rutting that is caused by vertical strain should be evaluated for unbound layer cross-anisotropy in the design and evaluation of pavements. Overall, strain responses due to cross-anisotropy are highly sensitive to AC layer temperature.

  • Supplemental Notes:
    • This paper was sponsored by TRB committee AFD80 Strength and Deformation Characteristics of Pavement Sections.
  • Corporate Authors:

    Transportation Research Board

    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Authors:
    • Ahmed, M U
    • Tarefder, R A
    • Islam, R M
    • Rahman, M T
  • Conference:
  • Date: 2014


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 18p
  • Monograph Title: TRB 93rd Annual Meeting Compendium of Papers

Subject/Index Terms

Filing Info

  • Accession Number: 01518137
  • Record Type: Publication
  • Report/Paper Numbers: 14-3588
  • Files: TRIS, TRB, ATRI
  • Created Date: Mar 11 2014 12:07PM