| Science its special geological structure background,the regions covered by loess in china which include the south-north Seismic belt,north of china seismic belt and Qi-Lian Seismic belt,is one of the regions with the maximum frequency of earthquake occurred in our country,and has the massive history strong earthquake records.For the reason of earthquake vulnerability,subsidence and liquation of loess,the history earthquake induced numerous of seismic geological disaster,especially the 1920 Hai Yuan earthquake,trigger a lot of loess landslides.This paper took the Xiajia road landslide in Xiji County of Ningxia province induced by Haiyuan earthquake for instance and made a research on formation mechanism of loess liquefaction landslide induced by earthquake.In the foundation of detailed geological data in the study area,The basic characteristics of landslide,the landslide area of loess liquefaction mechanism and the formation mechanism of landslide were studied by ways of field investigation,indoor test,theory analysis and numerical simulation method,etc.The results are as follows:(1)Xiajia road landslide is large seismic loess landslides formed during the 1920 Haiyuan earthquake of magnitude 8.5.Its original slow slope grade is 17°,its main sliding direction is 102°,its sliding distance is about 200 meters,its landslide volume is 130×104m3;(2)the loess' s basic properties and material composition of the landslide area were carried out by laboratory tests.Then this paper tested loess' s dynamic characteristics on the effect of random wave and got stress-strain relationship under the effect of random seismic waves,and it studied the difference of loess static anddynamic strength by contrast experiment and influence of saturation on the strength of loess;(3)After obtaining the evidence of landslide liquefaction causes on site,the liquefaction potential of Xiajia road landslide area was analyzed.The paper tested indoor triaxial tests of intact loess after the initial criterion of basic physical properties and getting the possibility of liquefaction.By simulating loess liquefaction of different depths in the random seismic loads,then this paper analyzed the loess liquefaction characteristics(including pore pressure,strain development curve and pore pressure-strain curve).Then it analyzed the liquefaction effect on its microscopic structure by electron microscope scanning experiments.At last,This paper proposed saturated loess liquefaction mechanism and explained the principles of effective stress and from Coulomb's law.(4)This paper got the loess' s saturation effect on liquefaction by the test results and analyzed the groundwater conditions of landslide area,then proposed landslide is due to the loess combining with seismic force conditions.Then the genetic mechanism of liquefied type loess landslides was detailed analyzed.(5)Combined with the actual situation in the landslide area and through FLAC3d(continuous media fast Lagrangian method)simulation software,the natural state of the slope in front of the slide,under the force of the earthquake force and deformation were analyzed.Then by using Chen Yumin's PL-Finn model which was developed on Finn model and can be used to calculate the soil liquefaction,this paper made liquefaction simulations on the slope,studied the deformation and made comparative analysis of the loess liquefaction's impact on the slope deformation after importing groundwater table.Finally,this paper made an explanation analysis of liquefaction loess landslides after the feedback of the numerical simulation results and the actual situation. |
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