地震波の周波数特性が山腹斜面の安定性に及ぼす影響に係る研究－周波数をパラメータとしたモデル斜面の動的解析－

抄録

Numerous studies have analyzed the relationship between seismic motions and slope stability. However, few dynamic analyses have been performed to study how differences of frequency characteristics of seismic waves affect the stability of natural slopes. In this study, we analyzed the effects of frequency by focusing on the two mechanisms : (1) the dependency of dynamic responses of natural slopes on the correspondence between the frequency range which intensify the dynamic response and the frequency characteristics of seismic waves ; (2) the dependency of indicative of slope stability on the amplitudes and frequency of responses (acceleration : A and velocity : V ). The dynamic analyses with sinusoidal wave, revealed that V correlates well with δ_r for the same A but different frequency. Furthermore, dynamic analyses with measured seismic wave suggest that if the spectrum is strong in the low frequency range, δ_r and shear stresses are greater than in the case with spectrum with strong component in the high-frequency range. This mechanism is consistent with the previous research which indicates that acceleration response spectrums, in the cases of high number of slope failures, show stronger components in the frequency range below 1.0 Hz than those of waves in the cases of low number of failures. Hence, the seismic wave with its strong component in the low frequency range (above 0.5 Hz) tend to induce large δ_r and shear stresses, then more likely to destabilize slopes, i.e., a higher risk of sediment disaster. Finally, we propose that frequency characteristics of seismic waves is one of the key factors in evaluating the hazard of slope destabilization.