Study Of Formation Mechanism And Later Trend Prediction Of Fanjiaping Landslide And Baishuihe Landslide

The paper choose the Fanjiaping landslide,Baishuihe landslide which are typical inhead region of Three Gorges Reservoir on base of the scene investigation and existingdata to carry research.With analysing monitoring data and regional structure of both twolandslides, we came to the conclusion that formation mechanism and deformation andfailure mode of these landslides. The analysis that the mechanical properties displayis obatained through the test on the reservoir water pressure and long-time circulationfunction of the reservoir fluctuation. And take the example of Baishuihe landslide toanalyse the long-term evolution trend.The formation mechanism and deformation and failure mode of these landslides areinvestigated by theories of the neotectonic movements,regional structure and concerningmechanism.The results show that the evolution of both landslides are controled byXiejiabao anticline which is thin-skinned structure. The failure mode of Fanjiapinglandslide is caused by gravity anticline,but the failure mode of Baishuihe landslide iscaused by shear failure. The evolution of both of these landslides are different inevolutionary process.The longth of landslide is a key factor when the factors such asattitude of rocks,angle of slope,combination characteristics of rock and soil are uniform.The critical longth of slope of gravity anticline failure is the decisive facter which causethe different failure mode.Based on the deformation process and stress characteristics of the landslideclassification, and then conclude the deformation law of these slides through a lot ofapparent landslide monitoring data of Fanjiaping (Muyubao) and Baishuihe landslide.Theresults show that Muyubao landslide is in the creep deformation now,all of thecumulative displacement curves of measuring points show the characteristics ofcontinuous growth, Baishuihe landslide is also in the creep deformation now,thecumulative displacement curves of measuring points show the characteristics of step-likegrowth;Muyubao landslide deforms by water level fluctuation in reservoir,it is lesssensitive to the facter of rainfall,it can be regarded as the water level fluctuation-inducedlandslide,Baishuihe landslide deforms by the factors of rainfall and drawdown, it can beregarded as both rainfall and drawdown-induced landslide.The paper choose the sandstone to take “immersion-drying” cycle conditions test,and use the way of numerical simulation to analyse the evolutionary trend of the landslideby under reservoir water circulation,the results show that during the cycle of“immersion-drying”test,the longitudinal wave velocity and uniaxial strength of sandstonesamples decrease gradually under different soaked conditions, the higher value of waterpressure, the more repidly the wave velocity and uniaxial strength decrease; during thecycle of “immersion-drying”test, the deterioration effect of uniaxial strength becomesstronger with the the soaked cycle going on;the difference isn’t obvious after one month,but the difference under different conditions is between15.7%and27.1%afetr sixmonthes;the landslide will be instable from deformation stage to movement stage afterthe fluctuation of water level in reservoir area(30m amplitude) cycles73times,thelandslide revived,the rock mass parameters are that φ=16.3，c=0.23MPaat this moment;the simulative trend is coincident compared with monitoring value,it verifies theprevious analysis and judgment.