Research On The Stability And The Displacement Response Ratio Of Dynamic Increment Of Landslide Under The Condition Of Reservoir Water Level Drop

On the premise of great diversity of topography,geological structure and hydrodynamic conditions,the geologic hazards in the Three Gorges Reservoir Area have been sustaining high incidence.The accumulation landslides are widely distributed.Plenty of cases indicate that the occurrence of landslide instability in reservoir is triggering the stage of reservoir water level decline and the main factors affecting slope stability are internal and external hydrodynamic coupling parameters k/v(The ratio of the permeability coefficient in slope and level drops rate out of slope)and the morphological elements of the slope(slope shape,slope angle and thickness of accumulation layer).There are many methods for evaluating slope stability,but a new one remains demanded.Therefore,study on the stability under the condition of water levels fall and the regularity of displacement response ratio of dynamic increment has a crucial practical significance and value for the Three Gorges Reservoir Area and even the whole country,landslide hazard prediction and prevention around the world.This paper taking the accumulation landslide in the three gorges reservoir area as a research object,researches on the evolution characteristics of the field of seepage,stress,displacement and stability via theoretical analysis,orthogonal test and numerical simulation,besides,displacement response ratio of dynamic increment is introduced to predict the instability.Through the above analysis,the following conclusions can be obtained:1.The factors influencing the seepage and stability of wading slope are classified as k/v and slope form elements.By the statistics above,high-frequency parameters can be gathered.Using the finite element software GeoStudio and saturated-unsaturated seepage theory,the characteristics of the above factors on seepage velocity,seepage pressure,displacement field and stability coefficient will be gained.2.Based on the orthogonal test idea,the most representative points selected from many test points by orthogonal table are devoted to the typical experiment simulation.Then,through sensitivity sort of the factors affecting the seepage velocity,seepage pressure,displacement and stability coefficient to get k/v that the most significant factor whose variation leads to the most obvious evolution of slope stability.3.According to the black box theory,in order to analyze dynamic factor andresponse characteristics of the slope and summarize the regularity of its stability,this paper introduces a parameter,nonlinear dynamics displacement response ratio of dynamic increment,and establish the quantitative relationship of the damage modulus parameter in the damage mechanics and slope stability coefficient.Thus,the slope body damage evolution rule of instability could be described quantificationally.4.Regarding the reservoir water level drop range as dynamic loading parameter,coupled seepage-stress analysis of the landslide slope will be carried out that the displacement of the equipotential line even the size distribution and change rule of the displacement of landslide can be determined.Afterwards,combining the displacement above and the change rule of reservoir water level to analyze,it can be gathered that the displacement response regularity of dynamic increment.Consequently,the feasibility and validity of this parameter in landslide stability evaluation and landslide prediction are verified.5.Landslide deformation stages could be divided by displacement response ratio of dynamic increment: When displacement response ratio of dynamic increment fluctuates slightly in the neighborhood of 1,the slip region is in the elastic deformation stage;When the parameter deviates 1,the slip area is on the stage of elastic-plastic deformation;When the parameter increases sharply,the slip area is in the plastic deformation stage in the meantime the landslide will collapse soon.6.Eventually,taking the Shuping Slope located in Shaxi Town,Zigui County,Yichang City as an example,this chapter regards the reservoir water level from 175 m to145m as an increase cycle.On the one hand,referring to reservoir water level and displacement or displacement velocity of Shuping Landslide as dynamic loading parameter,The displacement response ratio of dynamic increment time series curve of this loading cycle can be obtained in order to judge the dangerous water level in the water drop stage and provide evidence for water level regulation and landslide prevention.On the other hand,the stability coefficients of the load cycle are calculated by finite element simulation software.these couple of time series curves show the exact opposite trend that proves the applicability and efficiency of the dynamic load displacement response ratio in the quantitative characterization of landslide stability.