Cyclic and Post-Cyclic Response of Compacted Coal Ash

In the present study, effect of shear strain amplitude and frequency on cyclic and post-cyclic response of coal ash was investigated under simple shear conditions. A series of multistage tests on coal ash specimens including strain-controlled cyclic loading and post-cyclic undrained monotonic direct simple shear tests were conducted. Another series of undrained monotonic direct simple tests on coal ash specimens without cyclic loading history was also carried out to evaluate the effect of prior cyclic loading on post-cyclic response of coal ash. The results depicted that the shear modulus was found to be decreasing with loading cycles for coal ash specimens on increasing the cyclic shear strain amplitude except 0.01%. The damping ratio was observed to be increasing with loading cycles for shear strain amplitudes ranging from 0.5 to 1.5%. The effect of frequency indicated negligible shear modulus degradation behaviour on increasing the frequency from 0.1 to 1.5 Hz. However, greater shear modulus degradation was observed for specimens subjected to 2 Hz frequency. The post-cyclic stress–strain response indicated that coal ash specimens exhibited higher failure shear stress as compared to the specimens with no cyclic history. With an increase in the cyclic frequency, post-cyclic stress–strain response exhibited higher failure shear stress as compared to the specimen with no cyclic history.