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Repeated Load CBR Testing, A Simple but Effective Tool for the Characterization of Fine Soils and Unbound Materials

Almost all available design methods for low volume roads are empirical in nature and rely on simple input parameters like CBR for subgrade, subbase and base materials. There is however a strong need to use mechanistic based design analyses to check the empirical based designs on the consequences of e.g. overloading, unexpected poor material quality etc. In order to be able to use such mechanistic design systems successfully one needs to have information on the resilient and permanent deformation characteristics of unbound materials in relation to the degree of compaction and moisture content. Such information can be obtained through repeated load triaxial testing. These tests however, are costly and, especially in developing countries, equipment needed to perform these tests is not always available. This shows that there is a need for simple but effective characterization techniques allowing mechanistic based design systems to be used. This paper shows that the repeated load CBR test is a powerful tool to perform such a characterization for soils and unbound materials. After the introduction, a short description of the test will be given first of all. Then results of a finite element analysis are presented that show that it is indeed possible to obtain a fairly good estimate of an effective modulus Eeff by means of the repeated load CBR test. This is supported by the discussion of how the results obtained by means of the repeated load CBR test relate to the results that are obtained using repeated load triaxial testing. In conclusion it is stated that the repeated load CBR test is a simple and quick test to obtain good estimates of an Eeff in cases where repeated load triaxial data are not available and/or cannot be obtained. Also good correlations exist between the Eeff as determined by means of the repeated load CBR test and the Mr obtained from repeated load triaxial tests.

Language

  • English

Media Info

  • Media Type: DVD
  • Features: Figures; References; Tables;
  • Pagination: 22p
  • Monograph Title: TRB 87th Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01099665
  • Record Type: Publication
  • Report/Paper Numbers: 08-0516
  • Files: TRIS, TRB
  • Created Date: May 21 2008 7:10AM