The Centrifuge Model Test Forthe Deformation And Failure Mechanism Of Landslide Induced By Toe Excavation

With the accelerated construction of mountain highways,a large number ofartificial slopes formed,which often brings about landslide disasters.Now landslideinduced by toe excavation has become one of the main landslide disasters in ourcountry.Being an unloading process,slope toe excavation will have adverse effect onslope stability which is directly related to the safety,progress and budget of theconstruction.Owingto the exceptive of loess's material composition and engineering property,theformation condition and mechanism of loess landslide show thecomplexity andvariability.Therefore,it is necessary to do detailed researches on this landslideinduced by slope toe excavation and determine its instability mechanism.In this paper,the typical landslide induced by toe excavation,Yangyalandslide in Yanan is the main research object.On thebasis of field investigation and data collection,deformation and failure mechanism of typicalexcavated loess slope will be research by laboratory tests,the centrifuge model testand numerical analysis.The concrete content is as follows:(1)Through field geological investigation and indoor physical and mechanical tests,we identify Landslide's deformation characteristics,and analyse the unstable factors and the degree and the way of the influence.The results show that,the structure character of loess is the first factor of this landslide,while the excavation of the slope's toe and the rainfall's infiltration is the most important triggered-factor of the landslide.At the same time,the confining pressure's unloading stress path(i.e.,slope toe excavation)caused the change of the loess's stress-strain's development characteristics and the intensity.(2)Through the design and implementation of centrifuge model tests,the slope's development of deformation and damage in the original state,the excavation state and the rainy state is simulated.The slope's stress-straindevelopment in the process of deformation and failure is gained through the analysis and comparison of experimental results within the slope's distribution of displacement and the process of change and the changes of the soil pressure in slope,And then we can reproduce the process of deformation and failure and research its instability mechanism.The results shows that:the excavated slope's excavational free face collapsepartially,and the displacement decreased from the toe to the trailing edge,the potential slipsurface,plastic zone and tension fractures on slope's surface are developed from the bottom to the top gradually,the interior of the excavated slope's stress significantly decreased,and the unloading effect is obvious when it is closer to the excavation face.(3)The stress and strain of slope before and after the excavation process of deformation and destruction can do numerical analysiswith FLAC,including the initial stress field,the change pattern of stress and strain after the excavation process of deformation and destruction,and the development process of shape of failure zone.Combined with the field investigation and centrifuge modeling testthe characteristics and mechanism of the landslide deformation and failure can be analyzed and compared.It can be conclude that the deformation pattern is typical pull-type deformation failure mode and geological mechanics model is slip-press to cracking.(4)Through comparing and analysis of stability calculation method,strength subtraction method can be chosen that the safety factor is 1.161before excavation,and is 1.046 after excavation.Before the excavation the slope stay stable state and after the excavation the slope stay unstable state.The excavation of slope toe had a bad influence on the stability of slope seriously.