The mechanistic–empirical pavement design guidelines recommend the use of the material modulus in lieu of the structural number for the design of pavement base layer thickness. The modulus is nonlinear with respect to effective confinement stress, loading strain, and moisture (suction). Modulus nonlinearity should be considered for an efficient base layer design and analysis. Fixed-free resonant column tests were conducted on two base materials used in Florida to characterize shear modulus (G) nonlinearity in the strain range of 10-5% to 10-1%, including small level strains, under different loading confinements and moisture contents. The suction effect on the nonlinear modulus due to drying was evaluated, and it was found that the unsaturated modulus was linear at strains lower than 10-5% and nonlinear thereafter. In a comparison with dry materials, the presence of moisture in unsaturated material made it more nonlinear with respect to strain. The suction effect increased G in the strain range of 10-5% to 10-1%, with significant increases at strain levels below 10-3%. Empirical equations were developed to calculate the very small strain modulus (Gmax) of dry material. A procedure to calculate an approximate G-value at known moisture content, confinement, and strain magnitude was developed.
Characterization of Moisture-Dependent Changes in Stiffness of Unbound Aggregate Base Materials in Florida
Transportation Research Record
Transportation Research Record: Journal of the Transportation Research Board ; 2349 , 1 ; 25-31
2013-01-01
Article (Journal)
Electronic Resource
English
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