| “5.12” Wenchuan earthquake induced a lot of slope deformation damage, it showmany dynamic characteristics, the most unique and serious hazard is rock avalanche.Therefore, analyses of slope in earthquake dynamics under the action of the responsecharacteristics are particularly important.The more typical landslide in Qingchuan County triggered by the Wenchuanearthquake is Donghekou huge landslides. With the seismic force the top of thelandslide which range from elevation1070m~1330m along NE55°invadingprojectile out.it hit the left front which the elevation about1050m, disintegrated intodebris flow and resulted in the tragic loss of780people were killed.For such large-scale landslide material invading the phenomenon, this article willbe based on field investigation, the dynamic characteristics, seismic wave spectrumanalysis, and combination of numerical simulation to study the dynamic response ofof Donghekou landslide under seismic action characteristics. The main researchresults are as follows:（1）We use modal analysis capabilities of ANSYS software to study the naturalfrequency of the slope model; Harmonic response analysis to determine the naturalfrequency of the selected in that order natural frequency excitation resonance basedstudy; the first natural frequency is about0.56Hz. And then we analysis the factorswhich are affecting the inherent frequency, such as elevation, slope, density, elasticmodulus, poisson’s ratio, the study found its natural frequency were positivelycorrelated with slope, elastic modulus and negatively correlated with slopeheight,density. We also found that slope height and elastic modulus have more impacton the natural frequencies obviously than other factors.（2）The acceleration record from the Guangyuan station, we can get the Fourierseries coefficient through fast Fourier transformation.We will transform discrete acceleration records into the function expression for the acceleration versus time.Based on this expression, we are using SeismoSignal Software to analyse thespectrum of seismic wave acceleration. The Fourier value spectra showed that thefrequency component of maximum amplitude is about2.8Hz in the original wave,Fourier power spectra show that0-10Hz band in a dominant position in the seismicwaves.（3）Through the field investigation in Qingchuan County, geological hazardsextend along the faults and distribute in the intersection of fault structures; becausethe dynamic effect, the aspect which have the same direction with seismic wavepropagation are prone to have geological disasters; most hazards occurred in thehighness of less than300m; The slope has clearly earthquake response in the range of30°~50°,in which number accounted for91%of the total; Seismic waves hassignificantly dynamic response in the isolated ridge and the empty parts; Mountainpredominant frequency is mainly concentrated in the3~6Hz. If the main frequency islower than3Hz, the resonance effect between seismic waves and mountains will bestrengthening and the development of geological disasters will be increasing;（4）Under strong earthquake response, we used FLAC3Dsoftware to analyze theresponse characteristics and influence factors of Donghekou landslides. The results ofthe study show that: under the common function between horizontal and verticalseismic wave, acceleration have amplification effect in elevation and free surfacefactor. Amplitude of the response of acceleration in the soft rock is larger than hardrock; from the total seismic waves we detached natural frequency and predominantfrequency, which were0.56Hz and2.8Hz.we also found that seismic wave had abigger amplification effect in2.8Hz than in0.56Hz; The resonance effect in the roleof Donghekou landslide is not obviously in the Wenchuan earthquake, butpredominant frequency is the main reason to lead Donghekou landslide. We alsocombined with speed wave function of0.56Hz and2.8Hz, Further got that the natureof acceleration amplification is the effect of amplitude amplification. |
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