산사면의 지진동 증폭 특성

초록

Seismic stability of slopes is most often assessed through pseudo-static analysis or Newmark displacement method. In both types of analyses, it is necessary to define the maximum acceleration of the slope. It is current practice to determine the acceleration using the seismic site coefficients. However, the site coefficients are not compatible with slopes, since they were developed for horizontally layered soil profiles. In this study, a series of pseudo-static and dynamic analyses are performed on various mountain slopes, from which the amplification factors are derived. A new method for calculating the amplification factors is proposed in this study. In a slope, the ground acceleration varies in both the vertical and horizontal directions. In the proposed procedure, the calculated accelerations at each node inside the slope failure mass are summed. The amplification factor is defined as the ratio of the average acceleration of the soil mass to the rock outcrop peak acceleration. The factors calculated using the proposed method is shown to be close to 1 for mountain slopes modeled in this study. The factors are approximately 14 – 50% lower than coefficients developed for horizontal soil deposits. The derived factors are lower because even though the amplification at the slope crest is high, as well as on the surface of the slope, the amplification is low near the bottom of the soil layer. In summary, it is demonstrated that the use of the site coefficients derived for horizontally layered soil profile will lead to significant conservative estimate of the slope stability.

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