Evaluation of Subgrade Resilient Modulus from Unsaturated CBR Test

  • Aneke Frank IkechukwuEmail author
  • Mostafa M. Hassan
  • A. Moubarak
Conference paper
Part of the Sustainable Civil Infrastructures book series (SUCI)


Appropriate pavement design requires knowledge of stress-strain response of subgrade layer under cyclic loading. Pavement structure is generally under unsaturated conditions, above groundwater table (GWT). Thus, to appropriately design a pavement, it is significant to consider suction matric (ua − uw). Resilient modulus (Mr) is an important property that characterizes subgrade behaviour through repeated load triaxial test (RLTT), with relatively high reliable testing procedures. However, the nature of the RLTT procedure is costly, time-consuming, and somewhat complicated. To alleviate these constrains, this study focused on the application of conventional California Bearing Ratio (CBR) and unsaturated CBR for estimation of Mr values. Various equation in the literature for estimating Mr failed to consider suction matric. One of the mentioned equation in the literature was adopted to estimate Mr values and the estimated Mr values were compared with values estimated using proposed equation from unsaturated CBR testing with respect to experimental data from the three-compacted fine-grained soils. The limitations of these equations were assessed based on the comparisons between laboratory evaluated and estimated Mr values. The Mr values estimated from unsaturated CBR equation, closely predicted Mr of three subgrades with percentage error ± <5%. The CBR equation from the literature, overestimated Mr values of the studied soils with average percentage error of ± >50% respectively.


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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Aneke Frank Ikechukwu
    • 1
    Email author
  • Mostafa M. Hassan
    • 1
  • A. Moubarak
    • 2
  1. 1.Sustainable Urban Road Transportation (SURT) Research Group, Department of Civil Engineering and Information TechnologyCentral University of TechnologyBloemfonteinRepublic of South Africa
  2. 2.Department of Civil EngineeringSuez Canal UniversityIsmailiaEgypt

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