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| 1 | Study of Shaking Table Test on Dynamic Response Characteristics and Failure Mechanism of the Loess Slope显示文摘The natural loess that covers the ground surface has good stability due to its low water content.However,when violent earthquakes occur,the strong dynamic stress generated in the slope may induce landslide disasters with different sizes.In this paper,a large-scale shaking table model test is used to reveal the dynamic response and instability failure process of the loess slope.The test results show that different parts of the slope have different vibration characteristics and the first natural frequency in the model increases with the increase of the slope height.The response acceleration of different parts may change due to the coupling relationship between the spectral characteristics of input wave and the natural frequencies of different parts of slope,suggesting the characteristics of regional differential dynamic response.Under the condition of different dynamic response,stress state and boundary conditions of different parts of slope,a rapid microstructural damage,cumulative residual deformation evolution,and tension-shear coupling instability failure process may appear at the top of the slope with the strong dynamic response associated with the increase of dynamic loading intensity.The Sd values presented in this paper may reflect soil damage and slope instability and failure. | PU Xiaowu WANG Lanmin WANG Ping CHAI Shaofeng XU Shiyang | 2020 | Earthquake Research in China2020，34，1： | 3 |
| 2 | The response law of far-field seismic ground motion of the Wenchuan earthquake and its damaging mechanism in the Loess Plateau显示文摘A series of housing collapses and other serious damage was caused by the 2008 Wenchuan M_(S)8.0 earthquake in the seismic intensity Ⅵ areas of the Loess Plateau, which is hundreds of kilometers away from the epicenter, and which showed a remarkable seismic intensity anomaly. The seismic disasters are closely related to the seismic response characteristics of the site, therefore, the systematic study of the far-field seismic response law of the Wenchuan earthquake in the Loess Plateau is of great significance to prevent the far-field disaster of great earthquake. In this paper, the seismic acceleration records of several bedrock stations and loess stations from the seismogenic fault of the Wenchuan earthquake to the Loess Plateau were collected, and the attenuation law of ground motion along the propagation path and the characteristics of seismic response on the loess site are studied,and the mechanism of amplification effect of ground motion is analyzed based on the dynamic feature parameters of the loess site obtained through the HVSR method. Taking a typical loess site of thick deposit as the prototype, a series of shaking table tests of dynamic response of loess site models with different thicknesses were carried out.Amplification effect, spectral characteristics of acceleration in model sites were analyzed under the action of a farfield seismic wave of the Wenchuan earthquake. The results show that seismic attenuation on the propagation path along the NE strike of the seismogenic fault to the Loess Plateau is slower than that in other directions, and the predominant period range of ground motion on bedrock site of the Loess Plateau presents broadband characteristics. Because the natural periods of loess sites with thick deposits are within the predominant period range of bedrock input wave, loess sites appear significant amplification effect of ground motion, the horizontal acceleration of ground motion exceeds 0.1 g, the seismic intensity reaches 7°. The thicker the loess deposit is, the more significant the change of spectral characteristics of ground motion on loess sites, and the narrower the predominant period range of ground motion becomes, and the closer it is to the natural period of loess sites.Therefore, for some old houses on thick loess sites, the poor seismic performance and strong seismic response eventually led to their collapses and damages because their natural periods are very close to the predominant period of ground motion of the Wenchuan earthquake on thick loess sites;For these damaged high-rise buildings,the resonance effect might be the main reason for their damages because their natural periods are included in the predominant period range of ground motion of the Wenchuan earthquake on thick loess sites.These research results would provide a basis for seismic disasters prediction and evaluation and seismic design of construction engineering in the Loess Plateau. | Xiaowu Pu Lanming Wang Ping Wang Xiufeng Tian Shiyang Xu Shaofeng Chai Haitao Guo | 2022 | Earthquake Research Advances2022，2，3： | 0 |
| 3 | Experimental study on the influence of seismic subsidence of loess under bidirectional loading modes显示文摘Water content,dry density,void ratio,depth of soil layer,and seismic loading may all exert influence on the seismic subsidence of loess.Many scholars have carried out seismic subsidence tests of loess to simulate the stress on soil using unidirectional(axial)vibration instead of bidirectional vibration.We conduct seismic subsidence tests of loess using two different dynamic stress loading methods,unidirectional and bidirectional dynamic stress.In addition,the effects of different dynamic stress loading modes on the development of seismic subsidence of loess are compared for a case-study in northwestern China.The results show that(1)the increasing ratio of radial stress to axial stress has exerted significant influence on the seismic subsidence coefficient of loess under the loading mode of bidirectional dynamic stress(2)there is a critical ratio of radial stress to axial stress for seismic subsidence of loess,ranging from 0.6 to 0.8;when the ratio of radial load to axial load is greater than the critical value,the effect of bidirectional load on the development of seismic subsidence is more remarkable(3)when the ratio of radial load to axial load is smaller,the seismic subsidence of loess calculated by the existing unidirectional stress loading method is safe for engineering projects.However,if the value exceeds the safety ratio range it is dangerous to conduct safety evaluations using the seismic loess subsidence.The prediction value of seismic subsidence at engineering sites directly affects the later foundation treatment and the safety of the overlying structures.The seismic subsidence calculation and evaluation method in this study may provide a scientific basis for safety evaluations of loess sites in northwestern China. | Gaofeng Che Ping Wang Qian Wang Xiaowu Pu Jinlian Ma Shaofeng Chai | 2021 | Earthquake Research Advances2021，1，4： | 0 |
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