Effect of Non-Homogenous Slope Angles on Ground Surface Seismic Response due to Incident Vertical SV Waves

Source, site and path effect are three important parameters in ground seismic response in any area (flat surface and sloping surface). Site effect is a key parameter to study the evaluation of the seismic response of a hill or valley particularly in soil. Another important parameter is the soil layer combination in height of a hill, for example. In other words, appearing a loose and weak layer between dense soil layers, makes different seismic responses in comparison with a full homogenous slope in height. As we know in nature, there is not full homogenous slope or hill, so it is very important to study this problem in evaluating ground seismic response. We should take part soil slopes and rock slopes in seismic analyses. In this research, only non-homogenous soil hill is studied. We know that the slope angle has a clear role on the hill seismic response, so the amplification can be seen in top of the hill. It is clear that gathering energy in a bounded local area, top of the hill, can make a great response at top of the hill, as we call it, amplification. Amplification is related to different parameters such as soil layer parameters, geometry, slope angle, wave type and its characteristic as dominant frequency, and maybe so many other parameters that researchers have not studied yet. Another important civil engineering problem is construction on top of the slopes or near them. Therefore, in high seismic disaster areas, we may have large demolition of structures if designer has not implemented the site effect on his/her analysis. Recently, in 2800 Code (4th edition), topography effect is implemented in a simple table due to the slope angle to increase horizontal acceleration parameter. It should be noted that other different parameters may have great effect on ground seismic response and slope angle is one of them. In this research, effects of non-homogenous slopes’ angle on seismic response of ground surface due to the incident SV wave using FLAC 2D finite difference software are studied. Different parameters are used in this research. The numerical and behavioral model linear elastic is selected. In order to study the effect of non-homogenous slopes, slopes with different materials with 25, 30, 35, 45 and 60 degree are selected. In addition, dependence of slope angle with other slope height and incident wave frequency are studied. Obtained results show that the effect of slope angle on seismic response, in comparison with other studied parameters, are low and it may be neglected. Besides, it can be seen that changing the location of soil layers, does not have high effect on ground seismic response. The results show that the effects of slope angle in low frequencies and also low height are small on ground seismic response. Thus, increasing these parameters, frequencies and slope height, increases the effect of slope angle on ground seismic response. In this research, due to dependence of slope angle to slope height and incident wave frequency on ground seismic response, the effect of slope angle on amplification of non-homogenous slopes are studied based on different  (normalized height). In , the effect of slope angle on amplification response can be neglected. In other words in this condition the effect of slope angle is small but increasing , increase this effect. For  the amplification response in slopes with 25 degree is the highest in comparison with 30-degree slope. In addition, these results can be seen in 30-degree slope in comparison with 35-degree slope.