Anisotropy level prediction model of unbound aggregate systems

This study establishes a procedure to determine the level of anisotropy of unbound aggregate systems based on particle geometry, mechanical response and physio-chemical properties of the fine aggregate portion (particles smaller than 75 ) of the aggregate system. Stress induced directional dependency of material properties based on multiple variable dynamic confining pressure (MVDCP) stress path tests was determined for ten aggregate sources. Anisotropic responses for various gradations and saturation levels were determined for each aggregate source. The cumulative Weibull distribution function is used to describe aggregate size and aggregate geometrical characteristics. The fine portion of the gradation was characterized by the Rigden voids test and methylene blue test to account for fine particle shape properties and deleterious effect of plastic fines, respectively. Cross-anisotropic modular ratios are used as indicators of the level of anisotropy. The anisotropy model is developed based on a comprehensive aggregate matrix consisting of twenty seven aggregate features for sixty three aggregate systems. The sensitivity analysis of the model reveals the significant impact of particle geometry on level of anisotropy and orthogonal load distribution capacity of unbound aggregate systems. The model is also shown to be sensitive to the level of bulk stress and shear stress as reflected by the k2 and k3 parameters. 2008 Taylor & Francis Group, London.

Anisotropy level prediction model of unbound aggregate systems Conference Paper