| China is a country with many mountains and earthquakes occur frequently. Earthquake is an important factor leading to slope instability, collapse and landslide. Tens of thousands of slope failure events in the history is a result of the earthquake. In the past few years,theWenchuan earthquake(Ms8.0),Ludianearthquake(Ms6.5)and Lushan earthquake(Ms7.0) have occurred in our country. It shows that China’s earthquake fault zone, especially the Southwest earthquake fault zonein the relatively active period once again. With the implementation of the western development strategy of our country, many large projects need to be constructed.Among them, we will encounter many slpoe problems,especially the complex high steep rock slope problems. These slopes’ seismic response, deformation and stability issues are very prominent,and these become a major problem to be solved. Therefore,the research of high steep rock slopes’ seismic response characteristics undering earthquake has high scientific value and practical significance.The Wasi ditch paleoearthquake landslide is as the research object in this article. On the basis of checking out the relevant geological data,intensive field survey and indoor rock mechanics test, The author probed the formation conditions and mechanisms of the landslide. Combining the "11.22" Kangding earthquake monitoring data of Lengzhuguan slope, The authors analyzed the slopes seismic response characteristics of the study area.Finally, the authors explored the movement and response characteristics of the slope in history earthquakes through the method of numerical simulationinversion used toWasi ditch landslide. The main conclusions and understanding are as follows:(1)The research area is located in the northwest of Sichuan Province, the eastern edge of the Tibetan Plateau.It belong to the alpine canyon topography.The lithology is Jinning- Chengjiang plagiogranite. The geological structure mainly affected byXianshuihe, the Longmen mountains and Dadu river fault zone.The compressive stress direction of research area is NW-NWW,andthe tensile stress direction is NE-NEE.(2)The Wasi ditch landslide is located on the right bank of the Dadu River,the south coast of the Wasi ditch.Its average width of about 400 m, longitudinal length of about 700 m,average thickness of about 120 m and square about 3360×104m3.So it belongs to large ultra-deep accumulation landslide.The lithology of landslide deposits is plagiogranite.The slide source region is a convex mountain mouth with three facing empty.The rinku condition is good. The slide source area mainly developed four jointed surface,and local areas development overhead wedge "concave rock cavities".(3)The results of rock mechanics test of research areashow: area plagiogranite in natural state uniaxial compressive strength of about 70 MPa,the dynamic Poisson’s ratio of about 0.28,the dynamic elastic modulus of about 80.4GPa,the cohesion about 10 MPa,and the internal friction angle of about 60 °.(4) Through the ancient seismic landslide investigation and analysis,The factors of Wasi ditch landslide occurred are three facing empty landscape,jointed surface combinations,earthquakes and so on. The cumulative and trigger effects of the earthquake are the major factor for the slope instability and failure.(5)Throughresearching the earthquake monitoring dataof Kangding Ms6.3 recorded by 6 sets of seismic monitors located in Lengzhuguan slope. The results showed that the peak acceleration(PGA) of the right bank was significantly larger than the left bank, and its seismic energy(Arias intensity) was significantly higher than the left bank, and this phenomenon shows that the slope seismic response of the right bank was significantly stronger than the left bank. Acceleration response spectrum indicates that the damping characteristics of the site does not affects the seismic response curves. The seismic response strength will decreases with the damping increasing,but this change is tends to converge.That means the response intensity does not unlimited decline with damping increasing. The peak ground acceleration(PGA) and HVSR spectral ratio curves show that the amplification effect severely affected by terrain conditions. The amplification effect of thin ridge,on the right bank of Lengzhuguan, is significantly stronger than the alpine slope of the left bank. The amplification effect of 1# monitoring pointis obviously stronger than other monitoring points’.It explains that the Seismicresponseof the Multi-facing air mountain and the protruding parts of the mountain will be stronger.(6)The whole process of Research of Wasi ditch earthquake triggered landslides by DDA numerical simulation shows:in the process that the seismic waves propagate upward from the bottom of the slope, the peak ground acceleration will be amplified with the elevation increasing,and the amplification factor of up to 1.2 times. In the transverse plane, from the surface to inside of the slope, the peak ground acceleration of seismic waves will be amplified, and its magnification smaller than the vertical direction. |
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