Practical seismic fragility estimation of unreinforced and reinforced embankments in Japan

The seismic fragility of an embankment can be calculated considering the permanent seismic displacement obtained through the Newmark's sliding block analysis implemented using a Monte Carlo simulation with various soil and tensile strengths of the reinforcement. The above method is exact and precise; however, it has high calculation cost and is inefficient in practical tasks. This paper proposes a practical and straightforward method to estimate the seismic fragility of unreinforced and reinforced embankments subjected to earthquakes for practical seismic risk assessment. First, a strong seismic motions database adjusted by the Arias Intensity was created to calculate the seismic fragility of embankments. Then, the analytical models were implemented as unreinforced and reinforced embankment models with different embankment heights defined according to the railway design standard in Japan. The sensitivity analysis of the seismic fragility estimation of unreinforced and reinforced embankments was conducted with various embankment heights, average values of friction angle of the backfill soil, and tensile strength of the primary reinforcement. A practical and straightforward fragility curve estimation equation, with design parameters commonly used to check the embankment stability, is proposed for practical use.