Seismic reliability assessment of earth-rockfill dam slopes considering strain-softening of rockfill based on generalized probability density evolution method

This paper investigates the seismic reliability of earth-rockfill dam slopes under stochastic earthquake excitation considering strain-softening behaviour of rockfill materials. A new and efficient methodology that couples a recently developed generalized probability density evolution method (GPDEM) with a spectral representation-random function method is presented to assess the seismic reliability. To solve the GPDEM equation, the stochastic seismic responses analysis of a 242-m concrete face rockfill dam (CFRD) is translated into a series of deterministic dynamic calculations. The probability information and seismic reliability of the safety factor demonstrate that the results between the simulations considering unsoftening and softening behaviour of the rockfill materials become increasingly different as the earthquake intensifies, and strain-softening behaviour gradually appear under seismic excitation. Thus, considering the softening characteristic of rockfill materials, is of great significance to analyze the seismic safety of high earth rockfill dams. The traditional index for evaluating dam slope stability with safety factor is compared with a new index the cumulative time of the safety factor less than 1.0 (Fs < 1.0), suggesting that the new index is more reasonable to assess the seismic reliability of dam slopes. The results indicate that the GPDEM is an effective approach to seismic reliability assessment from the stochastic viewpoint and can directly reflect the failure probability.