Compression Index and Small Strain Stiffness of Six Coal Bottom Ashes in South Korea

This study investigates the small strain stiffness (G_max) of six coal bottom ashes in South Korea. One-dimensional compression tests using an instrumented oedometer cell were performed to measure the shear wave velocity (V_s), and the compression indices (C_c) of the six different bottom ashes were also explored in this study. The results demonstrate that, at low confinement, the C_c of bottom ashes are comparable to that of sand under a similar void ratio. However, at high confinement, the bottom ash shows very high C_c compared to sand due to the crushability of the weak and porous bottom ash particles upon confinement. The variations of α and β, which are V_s parameters (i.e., V_s = α (σ′_m/1 kPa)^β), with different C_c values of the tested bottom ashes are consistent with the existing empirical relationship. The G_max of tested bottom ashes can be adequately captured by the existing G_max estimating formula for angular sand, indicating that the G_max of bottom ash is highly comparable to that of sand with a similar void ratio and confining stress.