| After impoundment of the Three Gorges Reservoir, geological hazards such aslandslides and collapses happened in the reservoir frequently. According to relevantstatistics, there are several hundreds of grave and resurrection landslides around the ThreeGorges reservoir. The impoundment of reservoir will change geological conditions ofreservoir bank significantly, Especially cyclical fluctuations of reservoir water will greatlyaffect the physical and mechanical properties of rock and soil landslides, the landslide soilmass is often alternated between the state of saturation and unsaturation,some landslidesnearly reach to the edge of instability, If the reservoir water level change encounters strongrainfall, those landslides may fail. The analysis of the landslide’s revival mechanism underthe water level of reservoir and rainfall involving geology, hydrological condition,saturated-unsaturated soil mechanics and other multiform subjects, Due to the lack of data，No researchers has associated field monitoring data, interior and in situ soil mechanicstesting, numerical simulation for the research of typical reservoir-triggered landslide，so itis difficult to reveal the resurrection mechanism of wading landslide under the water levelof reservoir and rainfall.In this paper, the Shuping landslide in Three Gorges Reservoir was chosen as theresearch object, the theory of unsaturated soil mechanics is used to study resurrectionmechanism of Shuping landslide under the water level of reservoir and rainfall，Thefollowing works have been done in this paper:①we analyse the field macroeconomicinspections and monitoring data, acquiring the stability status and finite element simulationinitial conditions of Shuping landslide. By means of GPS monitoring data and applicationof time series analysis method, the forecasting model was established.②With Shupinglandslide saturated permeability test results and conventional physical laboratory testresults, and by using the software of Geo-Studio inversion program, the unsaturatedhydraulic parameters of Shuping landslide was obtained.③Establish3D geological modelof Shuping landslide, by using the finite element software ABAQUS, Shear strengthparameters of landslide is obtained by inversion of key points displacement.④Establishingthe Shuping landslide finite element calculation model that combined rainfall and reservoirwater. Geo-Studio numerical simulation software was used to discuss the Shupinglandslide’s revival mechanism under the water level of reservoir and rainfall.The rescults ofthe study are as follows:1)Analysis of the GPS monitoring data show that: In the active area of Shupinglandslide, GPS displacement curves are step-like. The movement at the middle part and toe of the landslide is much larger than that around the back scarp. During the past years, thelandslide moves faster when the reservoir water level goes down, while the movementslows down when reservoir water level rises. This shows the typical characteristics oflandslide dynamic water pressure. The drawdown of reservoir water level is the mainfactor of landslide deformation.the rear is in the compression deformation, thedeformation is mainly controlled by the reservoir water level fluctuation, and rainfall haslimited effect on the landslide. After the normal impoundment of the reservoir, thedeformation mode at the toe of the landslide is mainly the overall deformation. Combinedwith the GPS monitoring data and automatic displacement analysis, Shuping landslidedeformation is mainly the overall deformation, which shows the characteristics of tractivelandslide.2)By applying two moving average method to the total displacement of Shupinglandslide GPS monitoring point ZG85and ZG86, extracting its trend displacement, andgetting the corresponding periodic displacement term according to the total displacement,the trend displacement term is predicted using GM (1,1) of grey prediction model. Forperiodic term displacement usingAR ()autoregressive model, accumulated the trendprediction and the periodic term predictive value to get total forecast, And compared withthe measured value of the total displacement, The prediction results are basically consistentwith the test results, display the Shuping landslide deformation trend of increasing signs ofdeformation.3)Underground drilling water level monitoring data show that Shuping landslidegroundwater front remains in a consistent state with the reservoir water level fluctuation,but the rise of ground water level and decrease rate is less than the reservoir water levelfluctuation rate.This will cause the body appears to be conducive to the stability of thelandslide body hydrodynamic pressure of the landslide in the reservoir water level rising,When the reservoir water level fall, Landslide in vivo head difference will producedynamic water pressure which is not conducive to the stability of the landslide body.4)Selecting GPS monitoring points ZG85and ZG86of larger deformation in the maincross-section as well as ZG88in Effect of deformation area as key Shuping landslidedisplacement monitoring points. Establishment3D geological model of Shuping landslidebased on Shuping geological plans and sections landslide, using ABAQUS software to getInversion analysis of shear strength parameters C=17kP a，=18in Shuping landslide.5)Analyzing Shuping landslide seepage field, stress field and displacement field underrainfall and reservoir water changes by Geo-Studio software. The results show:①Waterlevel changes have an impact on mid-front of groundwater level in Shuping landslide. The trend of Shuping landslide groundwater level fluctuation and reservoir water levelfluctuations is consistent. Groundwater level lags behind the reservoir water level. Whenthe water level drops, the water table shows a convex trend. when the water level rises, thewater table shows a concave trend.②The dropped water level has a greater impact onstress and deformation of the lower part of Shuping landslide. Effective stress reductionand displacement increase are concentrated in mid-front of the landslide.Heavy rainfall haslarge impact on the stress field and displacement field in Shuping landslide, mainly in therear part of the landslide.③Shuping landslide stability coefficient is consistent with thetrend of water level fluctuations. When the water level drops, Shuping landslide stabilityfactor decreases; when the water level rises, the landslide stability factor shows an upwardtrend. This shows the typical characteristics of hydrodynamic pressure affected landslide,when the water level drops with50-year heavy rainfall, landslide stability coefficientquickly dropped below1.6)Shuping landslide occurs by the interaction of internal and external causes of thelandslide, The internal factors are the structure of slope and landslide structure, Theexternal factors mainly for the reservoir water level fluctuation and the effect of rainfall.The monitoring results and numerical simulations show that when the reservoir water levelfall, because of the low permeability coefficient, Lead to the decline of groundwater levellags behind the landslides of reservoir water level, make the waterhead difference betweenthe inside and outside, The hydrodynamic pressure Point to to the free surface of landslide,Will not be conducive to the stability of landslide, And the drawdown speed more quickly,the landslide deformation faster, At the same time, because the slope is steep, the lowerpart of the landslide slide, the upper part of the landslide is losing support, as the existenceof a traction. When the reservoir water level rising, pointing to the slope dynamic waterpressure conducive to the stability of the landslide body in certain extent. Due to the poorpermeability of landslide body, rainfall is extremely difficult to infiltration, and the maineffects surface soil of landslide, the monitoring results and numerical simulation show thatthese problems. Therefore, the drawdown of reservoir water level is the most importantfactor affecting the Shuping landslide stability. |
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