The Study on Earthquake-induced Displacement Analysis of Slope by Three-dimensional Numerical Simulation

• Main Authors: Hong,Jing-Zong, 洪景宗
• Other Authors: Chien,Lien-Kwei
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/ev5496

碩士 === 國立臺灣海洋大學 === 河海工程學系 === 107 === Taiwan is in the Pacific Rim seismic zone. The frequency of earthquakes is quite frequent, and large-scale earthquakes of disaster-causing type often occur. According to the statistical analysis of the Central Weather Bureau (Centre Weather Bureau of the Seismological Center, 2019), there have been 102 devastating earthquakes from 1901(Meiji 34, Guangxu 27) to the present. In the case of extremely high population density and the area of the plain is not enough, in order to increase the land use area, people gradually develop to the slopes. However, the stability of the slopes is not like that in plain areas, but also because of the steep terrain, disasters (as collapse, ground slip, etc.) often occur due to natural factors (as rainfall, earthquake) or improper use of humans. In the past, the relevant research on slopes mostly took rainfall infiltration and groundwater level as the main axis. There is no mature evaluation standard for the earthquake in the slope, and it was usually evaluated in two dimensions. Therefore, PLAXIS 3D was used to analyze the three-dimensional numerical dynamics of the stratigraphic characteristics of the study area in this study. In the analysis process, the seismic acceleration duration curve measured by the Centre Weather Bureau of the Seismological Center was used to set the seismic force load of the model to explore the slope sliding position. Exploring the distribution and distribution characteristics of the slope sliding area, and according to the concept of displacement caused by earthquake and the concept of critical displacement, discussion on the influence of seismic force on slope stability. This study is different from the past discuss the impact of disasters from a two-dimensional perspective. By use of 3D simulation is more comprehensive and more realistic. In the selection of seismic data, this study considers the historical strong earthquake data of Taiwan and selects the acceleration duration observed by the station in the adjacent study area and input it as a shear wave at the bottom of the model. Exploring the impact of different Seismic intensity on slope stability. According to the analysis results, it can be found that the max displacement is 0.88cm ~ 2.54cm when the seismic intensity is I=2 and I=3. And the seismic intensity is higher than 4. The max displacement is increasing to 12.14cm ~ 238.4cm, which is larger than the critical displacement (5cm ~ 10cm) studied by previous researchers. When an earthquake of intensity I=4 or higher occurs, a significant cumulative displacement is generated, and the potential sliding surface of the slope is in an unstable state. In this study, the concept of critical displacement (Dc) is used to judge the stability of slope. With Dc=10cm as the evaluation index, the instability of the slope under the action of seismic forces at all levels is analyzed and presented in the cumulative displacement cloud map. The result of the above I = 4 grades will appear unstable regions, and the unstable regions will gradually expand as the earthquake increases. At the same time, this study established three observation points in the A-A' section of the study area. It is found that the displacement of the slope top is significantly larger than slope middle and slope toe under the action of seismic force. The main reason is that the seismic wave propagates to the surface of the colluvium. At the same time, the texture of the colluvium is relatively soft relative to the rock layer. After the seismic wave enters the colluvium, the wave velocity will slow down and the amplitude will be amplified. Some of the seismic waves will be reflected back into the slope and then continue to pass upward. At the same time, some of seismic waves will generate diffraction along the slope surface. As a result, the seismic wave gradually increases toward the top of the slope to produce an amplification effect, so that the displacement at the top position of slope is greater than the slope of middle and toe. Finally, this study uses the concept of three-dimensional and soil dynamic analysis to explore the effects of the process of three-dimensional seismic forces on the stability of slopes, which can further contribute to the study of geochemical three-dimensional numerical simulation of slopes. It can be an important reference for future government and scholars in the analysis of three-dimensional slope stability and prevention of landslide disasters.