Evaluation of the Effects of Topography on the Horizontal and Vertical Displacement of Semi-Sine Shaped Hills against Ricker Waves

Document Type : Propagative Article

Authors

1 M.Sc. Graduate of Geotechnical Engineering, Qom University of Technology, Qom, Iran

2 Assistant Professor, Department of Civil Engineering, Faculty of Engineering, Qom University of Technology, Qom, Iran

Abstract

This study presents the results of a numerical study on seismic behavior of two-dimensional semi-sine shaped hills that were subjected to vertically propagating incident SV wave of the Ricker wavelet. In the case of 2D response analysis of hills, different researchers studied the seismic response of triangular shaped hills under vertically propagating SH waves. Earthquakes are natural events that can have considerable economic and social injuries and have effects on people life and their environment. Geotechnical earthquake engineering has been noticed particularly in recent decades. Soil mass and soil structure response analysis against earthquake movements is one of the most important practical concepts in geotechnical earthquake engineering. This paper used finite difference method and represented that topography has specific effect on acceleration distribution in different points of roughness. The finite difference software is used to model and analyze the different sizes of the hills. Concentration is on topographic effects, so parameters such as the shape factor (the ratio of the height to half width of the hill) and the type of ground took into account in this research. The medium was assumed to have a linear elastic constitutive behavior. An important factor that affects on numerical results is the shape factor of the hills. Therefore, we modeled semi-sine hills with different shape factors (0.1, 0.4 and 0.8) subjected to Ricker wavelet with constant frequency on grounds with different properties that differ from each other in density and shear velocity (three types). The finite difference software used to run the numerical analyses was Flac 2D. The aim of this project was to investigate the response of topography effects on semi-sine shaped hills under Ricker wavelet, which is the second derivative of Gauss function. In this research, the horizontal and vertical displacements of different points on hills were calculated. Also, amplification factors were calculated from the ratio of horizontal components of motion to displacements of free-field model. The results are shown that both horizontal and vertical displacements were increased with a change in the shape factor as well as the amplification. It is shown that changing ground type from one to three, the displacements were reduced. Obtained results show that most horizontal displacement occurs in the top of the hill and as we reach the lowest height of the hill, this displacement decreases. Thus it can be seen that most amplification occurs in the top of the hill for different numerical models. The vertical displacement in top of the hill is zero and with decreasing the height of the hill, this vertical displacement increases and then decreases. Based on obtained results, the most vertical displacement occurs in the height between the top and down of the hill for different finite difference numerical models. Another important result is that these vertical and horizontal displacements depend mostly on soil geotechnical behavior of the hill. It is obvious that the shape factor of the hill affects on the obtained numerical results. An important factor that is studied in this research is the shape factor of the hill. Another important factor on which results are dependent is input motion frequencies. It is clear that when natural frequencies of the hill and the input motion frequencies are near to each other, the vertical and horizontal displacement increases. When the hill steep increases, the obtained results increase because of gathering most energy on top of the hill in a narrow band area.

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References

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History

  • Receive Date: 12 July 2020
  • Revise Date: 26 October 2020
  • Accept Date: 03 February 2021

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