Development of a saturation- and stress-dependent chord modulus model for unbound granular material

Show simple item record Van Aswegen, Elsabe Steyn, Wynand Jacobus Van der Merwe Theyse, Hechter L. 2016-01-15T06:54:48Z 2016-01-15T06:54:48Z 2015-06
dc.description.abstract Unbound granular material is used in the pavement structure and usually comprises the bulk of the structural and foundation layers of a typical South African pavement. The term unbound granular material refers to the classification of natural material, which has not been modified in any way. Unbound granular material is classified from a G1 to G10 quality according to its fundamental behaviour and strength characteristics. Young’s modulus and Poisson’s ratio are theoretical concepts of linear elasticity that can at best approximate experimental results of actual material elastic response. In their basic linear elastic form, Young’s modulus and Poisson’s ratio are rather poor approximations of actual unbound granular material behaviour. The non-linear, stress-dependent behaviour of unbound granular material can, however, be simulated using the linear elastic model as a basis, but with a proper constitutive material model that adheres to the observed material behaviour. The objective of this paper is to utilise a chord modulus model and calibrate it for a range of unbound granular material classifications. The model was calibrated for five bulk material samples, ranging from G2 to G8. The calibration process included linking variables of the model to mathematical functions that approximate the trends observed when variables were considered against degree of saturation. A parametric analysis indicated that the saturationand stress-dependent chord modulus model realistically predict material behaviour. The trends depict the stress-dependent behaviour of unbound granular material, where an increase in initial modulus is observed for increasing confinement pressure, as well as initial stress softening with increasing stress ratio followed by stress stiffening. It can be concluded from the results presented in this paper that a saturation- and stressdependent chord modulus model could be refined and calibrated for crushed and natural unbound granular material. This refinement did not negatively influence the accuracy or ability to realistically predict the material behaviour. The preliminary conclusions reported in this paper indicate that the chord model formulation yield satisfactory predictions, especially when the model is calibrated for each individual material type. en_ZA
dc.description.librarian am2015 en_ZA
dc.description.sponsorship The South African National Roads Agency SOC Ltd (SANRAL) and the Council for Scientific and Industrial Research (CSIR). en_ZA
dc.description.uri en_ZA
dc.identifier.citation Van Aswegen E, Steyn W J vd M, Theyse, H. Development of a saturation and stress-dependent chord modulus model for unbound granular material. J. S. Afr. Inst. Civ. Eng. 2015;57(2), Art. #985, 14 pages. 10.17159/2309-8775/2015/v57n2a2. en_ZA
dc.identifier.issn 1021-2019
dc.identifier.other 10.17159/2309-8775/2015/v57n2a2
dc.language.iso en en_ZA
dc.publisher South African Institution of Civil Engineering en_ZA
dc.rights South African Institution of Civil Engineering en_ZA
dc.subject Resilient behaviour en_ZA
dc.subject Model en_ZA
dc.subject Unbound granular material en_ZA
dc.subject Degree of saturation en_ZA
dc.title Development of a saturation- and stress-dependent chord modulus model for unbound granular material en_ZA
dc.type Article en_ZA

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