Centrifuge Modeling of Fly Ash Deposit Dewatering

Failures of fly ash impoundments have resulted in significant economic and environmental losses, with increased impacts due to the tendency for saturated fly ash to deform and 'flow'. Dewatering of fly ash ponds could potentially mitigate the risks associated with impoundment failure and the consequences due to fly ash runout. In this study, centrifuge modeling is used to explore changes to the bulk material properties of fly ash deposits resulting from dewatering. Changes to the water content across the deposit height were measured and linked to the measured suction in the pore fluid. These results were also used to estimate changes to the effective stress profile resulting from dewatering. A miniature CPT and bender elements showed that the fly ash shear strength and stiffness increase significantly as the water table was lowered within the model deposit. The potential improvement to the pond stability was highlighted by these centrifuge tests, with further research being undertaken to study the optimization of dewatering practices for ensuring both safety and economic feasibility.