| Since the completion of the Three Gorges Dam,many landslides in the Three Gorges Reservoir area have been deformed and damaged due to the periodic reservoir level regulation and rainfall.The main geological disasters in China are mainly concentrated in landslide,accounting for 73%of the total number of geological disasters.The accumulation layer landslide is.widely distributed,with serious hazards and high frequency,accounting for 80%of the landslide disasters.It is one of the representative landslides in many landslide geological disasters.The occurrence of this kind of landslides seriously affects the people's life and production,restricts the development of regional economy,and is also a problem of geological disaster control and ecological civilization construction in China.Therefore,it has important theoretical support to carry out the activity analysis,stability research and displacement prediction for landslide prevention and control.Firstly,the paper makes a statistical analysis of 30 typical accumulation landslides in the Three Gorges Reservoir area,and analyzes the development characteristics of accumulation landslides from the aspects of landslide scale,topography,stratum lithology and slope structure,focusing on the relationship between reservoir water fluctuation and displacement deformation curve,and the relationship between the activity of accumulation landslides and external induced factors;then,taking Baijiabao Landslide as an example,through the analysis of The analysis of the macro deformation and displacement monitoring data of the landslide,the deformation characteristics and formation mechanism of Baijiabao Landslide under the influence of external factors,the study of seepage field,displacement field and stability of Baijiabao Landslide under different drawdown rate of reservoir water level by using the numerical software geo studio,the verification of the deformation characteristics analysis by using the numerical simulation results,and the establishment of time sequence finally A series of models are used to predict the displacement of landslide.The main research results are as follows:(1)According to the statistical analysis of 30 typical accumulation layer landslides in the Three Gorges Reservoir area,the landslides are mainly large-scale landslides,large-scale landslides,followed by medium and small-scale landslides;most of the landslides are in the range of 20-30°;from the perspective of the failure mode of landslides,it is mainly the number of push type landslides;the most developed stratum is the Middle Triassic Badong Formation(T2b);the most of the medium thick accumulation layer landslides;Tongtong According to the analysis of typical accumulation layer landslide activity,one of the main factors affecting the development of landslide deformation is the fluctuation of reservoir water level.Most of the landslide deformation has lag phenomenon,the longest lag days are about 4 to 5 months,the shortest are about 4 days.A few of the landslide deformation is affected by the rise of reservoir water,and the deformation is caused by the immersion of high reservoir water.There is no lag phenomenon in this kind of landslide A small number of landslides are directly controlled by rainfall,which is easy to occur in the case of sudden rainfall and continuous rainstorm in flood season.(2)Taking Baijiabao Landslide as the research object,the macro deformation analysis shows that the landslide has been slowly deformed.The deformation on the left side of the landslide is smaller than that on the right side,and there are tension cracks on the back edge,some cracks on the right side are connected,and bank collapse appears on the front edge.The main inducement for the increase of landslide deformation is the decline of reservoir water,while the rainfall only plays a role in promoting;through the analysis of displacement monitoring data,it is known that the larger the decline rate of reservoir water level is,the larger the deformation rate is,the more the landslide displacement is,the higher the reservoir water level is,and the accumulated displacement deformation almost stops.Through the analysis of borehole groundwater level data and reservoir water dispatching data,the period after the decline of reservoir water level is The landslide deformation started only after 25-35 days.(3)Baijiabao Landslide Mass has low permeability.In the process of reservoir water level falling,the groundwater level in the slope body is too late to reflect the reservoir water falling.The larger the hydraulic gradient is,the more the landslide deformation increases,the lower the landslide stability is.When the reservoir water rises,the landslide deformation is small,which is beneficial to its stability.The reason is that the rising water level provides the floating support force for the landslide mass.According to the numerical simulation analysis,it is concluded that,The pore water pressure of the front edge of the landslide is far greater than that of the back edge.The reservoir water mainly affects the front edge of the landslide.The larger the rate of reservoir water falling,the larger the deformation of the front edge is,and the smaller the deformation of the back edge is.With the decrease of the reservoir water level,the stability coefficient of the landslide decreases all the time.With the increase of the descent rate,the probability of landslide failure is higher,so it is necessary to strengthen the monitoring(4)The accumulated displacement of Baijiabao Landslide can be regarded as non-stationary time series.Firstly,the difference method is used to stabilize the displacement series,and the accumulated displacement data from 2007 to 2012 is selected as the calculation sample.Using the time series analysis in the data mining method of SPSS software,the ARIMA model is established to predict the displacement trend of the landslide.The fitting degree of the model R2=0.863,which has certain accuracy.The model The displacement trend of landslide can be well reflected by the model.Figure[50]table[6]reference[59]... |
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