Study On Deformation Mechanism And Sensitivity Of Influencing Factors Of Bazimen Landslide In Three Gorges Reservoir Area

The Three Gorges Reservoir has been filling since June 2003,the water level in The Three Gorges Reservoir has risen from 145 m to 175 m.Geological disasters within the reservoir area are frequent,especially landslide disasters,which cause great economic losses and casualties.In this paper,the Bazimen Landslide in the Three Gorges Reservoir area is taken as the research object.According to the landslide investigation report and professional monitoring data,the deformation mechanism and deformation characteristics of the landslide are studied and analyzed.Combined with the geo Studio software,the numerical simulation is carried out to analyze the change rule of seepage field and stability coefficient in the landslide body under different water level rise and fall rates and rainfall conditions,and using the orthogonal experimental design method of mathematical statistics,to take sensitivity analysis about the landslide stability influence factors.The research contents and results are as follows:1)Combined with the professional monitoring data and investigation report of Bazimen Landslide in 2004-2018,the impact of the fluctuation of reservoir water level and atmospheric rainfall on the landslide is studied and analyzed,and the following conclusions are drawn:(1)the deformation and damage degree of the middle and rear part of the landslide is greater than that of other parts.(2)The overall displacement of the landslide is a typical "Step" type of increase,the annual overall displacement of the landslide in May to July increased sharply,during this period,the monthly displacement of the landslide is generally about 50 mm,the maximum can reach about 170mm(June-July 2012),the other months of the same year,the landslide displacement is small,the monthly displacement of the landslide are below 20 mm.(3)During the period of rapid increase of landslide displacement,the reservoir water level is in the stage of rapid decline,which has a high degree of coincidence in time(4)The increase or decrease of rainfall will not necessarily cause the increase or decrease of landslide displacement,for example: In 2009,the annual rainfall is about 863.6mm,the annual displacement of the landslide is about 250mm;In 2015,the annual rainfall reachs 1234 mm and the annual displacement of the landslide is about 150 mm.Rainfall has an "auxiliary" effect on landslide deformation.2)Because the water level of the Three Gorges Reservoir area is rising and falling rapidly and slowly,the former is set as 0.6-1.2m/d,and the latter is set as 0.5-2m/d when the landslide is in the period of falling and rising.The results show that when the drawdown rate of the reservoir water level rises from 0.6m/d to 1.2m/d,the phreatic line in the landslide will form a certain height head difference with the reservoir water level outside the slope,which will produce the hydrodynamic pressure effect pointing out of the slope,and the enhancement range of the hydrodynamic pressure effect will increase with the increase of the drawdown rate of the reservoir water,at this time,the stability of the landslide will gradually decrease;the water level in the reservoir will increase In the rising period,when the rising rate of reservoir water level rises from 0.5m/d to 2m / d,it will produce the hydrodynamic pressure effect in the slope.The increasing range of hydrodynamic pressure effect will increase with the increase of the rising rate of reservoir water,and the stability of landslide will increase.3)Based on the orthogonal test design method,the internal friction angle ? and cohesion c,the rise(fall)rate V of reservoir water level,the sliding weight degree H,rainfall T as the influencing factors,the stability coefficient Fs as the evaluation index,the sensitivity analysis of the landslide was carried out using the orthogonal experimental design method.The analysis results show that: when the reservoir water level is in the period of rising of low water level and falling of high water level,the stability of the landslide is more sensitive to the internal friction angle ? and cohesion c of the soil in the sliding belt,and the rate of rising(falling)of the reservoir water level V than the others;While the stability of the landslide is not same to the gravity of the sliding body ? and the rainfall t.