Liquefaction response of pond ash with varying bottom ash content

Abstract

The deposition process of ash slurry in the disposal site results in segregation of bottom ash and fly ash particles. Pond ash collected from different locations of the same disposal site can have varying proportions of bottom ash and fly ash particles. The present study evaluates the effect of varying bottom ash content on the liquefaction response of pond ash. A series of stress-controlled cyclic simple shear (CSS) tests were performed on pond ash with varying bottom ash content (0%, 20%, 40%, and 50%). The loading cycles were applied in the sinusoidal form at 1 Hz frequency and 0.12 cyclic stress ratio (CSR) under 100 kPa vertical overburden stress. All the specimens were prepared at their respective 95% maximum dry density (MDD) and optimum moisture content (OMC). The number of loading cycles required to liquefy the specimen was evaluated based on two criteria: i) Excess pore water pressure ratio, ru≥0.9, and ii) Double amplitude shear strain, γDA≥7.5%. Dynamic properties such as shear modulus (G) and damping ratio (D) were also evaluated for pond ash with varying bottom ash content. It was observed that the liquefaction resistance increased with an increase in bottom ash content. The generation of shear strain with the number of loading cycles was found to be more gradual with an increase in bottom ash content. The specimen with 0% bottom ash content showed a sharp decrease in shear modulus with an increasing number of loading cycles as compared to the specimen with 50% bottom ash content.