Study On Dynamic Response And Failure Mechanism Of Loess Slopes

The analysis of slope stability under earthquakes has always been a hot topic in the field of anti-seismic geotechnical.Studying the dynamic response and failure mechanism of the slope can provide better seismic guidance for it.As we all know,the accumulation of damage or deformation will lead to changes in the state of the soil.Based on this,two shaking table tests were used to study the seismic failure process of the loess slopes with different gradient,and different states caused by accumulation of damage or deformation were introduced to divide the slope failure process into several stages,thus the law of PGA and AFA changed with elevation at each stage were analyzed.The method of Wavelet Packet Transform(WPT)is introduced to analyze the response acceleration signal,and more detailed spectrum information was studied by MATLAB programming.The may research contents and results are briefly described as follows:(1)It was found that the failure forms of gentle slope and steep slopes were respectively suddenly and progressively after two shaking table slopes with the different earthquake failure processes were studied.The failure processes of the two slopes were divided into several stages respectively according to the accumulation of seismic damage to soil,based on which PGA and AFA at different stages were studied.It is concluded that the magnitude of amplification effect is different at different stages,and the state of slope is failure or not can be judged by the variation of PGA elevation law.(2)The Wavelet Packet Transform was used to analyze the acceleration signal and the energy proportion of each frequency band was extracted.The results shows that the earthquake wave of low-frequency components(0.1~12.51Hz)plays a leading role in the failure process.Through the fitted curve of the data scatter plot,it is found that no matter which kind of failure forms the slope is,the energy ratio E1 of the first frequency band always gradually decreases along the elevation,and the energy ratio E2 of the second frequency band gradually increases along the elevation.However,the elevation laws of E1 and E2 are obviously different at different stages,so it is feasible to judge whether the slope is failure or not according to the changes of the elevation laws of E1 and E2.(3)The response spectra of acceleration signals at different failure stages of the two slopes with different gradient were analyzed,and it is found that with the excitation acceleration increases the amplitude and characteristic period of the response spectrum will change significantly when the damage to soil accumulates to a certain extent,however the characteristic period will always be included in the main frequency range of 0.1 ~ 6.26 Hz regardless of how it changes after being converted to the vibration frequency.The conclusion verifies the relevant findings of the wavelet packet analysis section.(4)Considering the different degree of damage to soil at different stages,the differences and similarities between the two slopes with different failure forms were found by analyzing and comparing their behavior in earthquake,the elevation laws of PGA and AFA,the elevation laws of E1 and E2,and the response spectra of the acceleration signals.Then,the failure process of slopes under the two failure forms was explained from the perspective of the change of energy ratio,and their seismic failure process was divided into several stages officially.(5)Finally,the previous researches were cited and developed.Based on the above studies,the dynamic failure mechanism of the two types loess slopes was explained.