Seismic Response of A Large Deep-seated Rock Slope Revealed by Seismic Monitoring and Geological Surveys

In order to better understand the influence factors of the seismic response of the deep-seated unstable rock slope, we installed four high-sensitivity three-component integrated seismometers on Shidaguan slope (SDG slope) in Mao County, Sichuan Province, China. One of the seismometers was located at the stable part of SDG slope and at the highest elevation, while the other three were located in the deformation area of SDG slope. Nearly 100 sets of shallow source seismic data were acquired over a three-year period of seismic monitoring. Meanwhile, we carried out a detailed geological surveys by electrical resistivity tomography and drilling. Taking the monitoring point located at the stable part as a reference point, the peak acceleration obtained by the three seismometers located in the deformed area was compared to it. By this way, it is revealed that the seismic response of the reference point was the weakest, although it was at the highest elevation. The same phenomenon was obtained using the spectral ratio horizontal-to-vertical component of the seismic records (referred to here as HVSR). This is because that the fractured rock mass can act as a resonator, causing standing waves to develop in the broken rock mass. And the surface, as a free face, could show the strong ground shaking response. At the same time, we found that the seismic response was different for the three monitoring points in the deformed area of SDG slope. The seismic response of the deformed body with large thickness is smaller than that of the deformed body with small thickness. In order to analyse the reasons for the different amplification, we discussed the relationship between the amplification and the physical properties of rock mass. Rock mass with low resistivity and RQD caused seismic response amplification. However, this amplification was suppressed by that rock mass which exhibits viscoelasticity. The amplification of the ground shaking response would be influenced by the lithofacies difference degree in unstable areas, which should be taken into account when constructing buildings in landslide-prone mountainous areas.