Permanent displacement characteristics of landslides taking into consideration the frequency and energy behaviour of historical seismic ground motions

Abstract

Landslides often occur along motorways in earthquake-prone areas, leading to casualties and the loss of property. Most previous studies have applied the simplified Newmark method to assess landslide susceptibility at a regional scale, ignoring the characteristics of local ground motions. In this study, we investigated permanent displacement characteristics of three potential landslide areas along the Dayong Expressway using the rigorous Newmark method that considers the frequency and energy characteristics of historical seismic waves. First, the frequency characteristics of historical earthquakes in the study areas were analysed using the fast Fourier transform method and were adopted as input ground motions in calculating the Newmark displacement. Next, the critical accelerations of the three study areas were computed. Parameters such as the elevation, soil layer thickness and soil strength that are required for critical acceleration calculations were obtained using high-precision ( c. 3 cm) unmanned aerial vehicle mapping technology, drilling operations and laboratory tests. Finally, the Newmark displacement was calculated and the landslide susceptibility of the study areas was evaluated. The results showed that the predominant frequency of historical seismic waves in the study areas was 0.38–3.36 Hz, indicating low-frequency characteristics. The results also indicated that the frequency and energy characteristics of the seismic ground motions significantly influenced the Newmark displacement. The maximum Newmark displacement under different waveforms at Damieju ranged from 2 to 18 cm. Under the most dangerous conditions, all three areas showed a potential for landslides. The maximum Newmark displacement positively correlated with the energy of the predominant frequency. The large-energy and low-frequency characteristics of the seismic wave correspond to a large displacement. The simplified Newmark method when used in regional landslide susceptibility analysis did not reflect this effect and may be unsuitable to determine the size of landslides.