Small to intermediate strain properties of fly ashes with various carbon and biomass contents

摘要

High-carbon-content fly ashes with biomass particles are typically landfilled in accordance with the ASTM C618 regulation. To quantify their geotechnical properties relating to storage and disposal, this study evaluates the small to intermediate strain properties of fly ashes with various carbon and biomass contents. Tested fly ashes had carbon contents ranging from 1.1% to 9.6%, resulting from co-combusting coal with biomass (biomass contents ranging from 0% to 8.2% by weight). The small-strain stiffness and intermediate-strain constrained modulus were evaluated using consolidation tests performed in a modified oedometer cell equipped with bender elements. It was found that initial void ratio governed the compressibility (or constrained modulus) of fly ashes, and with an increase in carbon and biomass contents, the small-strain stiffness of fly ashes decreased due to the decrease in number of direct contacts between microspheres. In addition, the interfine void ratio, e(f), was employed instead of global void ratio to capture the alteration of interparticle contact or interparticle coordination between microspheres, due to the change in carbon and biomass contents. Finally, the stiffness in an overconsolidated state and the stiffness anisotropy of fly ashes were evaluated.