Abstract:The dynamic behavior of filling fly ash in ash storage dams is critical for evaluating the dynamic stability of ash retention dams under seismic action. In order to investigate the dynamic deformation and strength characteristics of filling fly ash, the dynamic stress-strain relationship, dynamic strength, damping ratio, and dynamic pore pressure of two types of specimens, i.e., saturated sedimentary ash and flushing ash, were tested by a hydraulic control dynamic triaxial apparatus under conditions of anisotropic consolidation. Results showed that the backbone curves of specimens showed a strain-hardening tendency, which can be an approximate hyperbolic relationship. In addition, the increase in vibration cycles will cause a decrease in dynamic sample strength, and is mainly related to the decrease in the dynamic cohesion rather than the internal friction angle. In the double logarithmic axis, the damping ratio after dimensionless treatment showed a linear relationship with the dynamic shear modulus, but was not closely related to the confining pressure. Under differing confining pressures, the dynamic pore water pressure changed only in a narrow range with increasing vibration cycles. For convenience of calculation, the influence of confining pressure and vibration cycle on the dynamic pore pressure can be neglected. Accordingly, the Finn formula can be used to describe the dynamic pore water pressure of fly ash specimens under anisotropic consolidation.