| The Yangtze River Three Gorges starts from Fengjie County in Chongqing City in the west and ends at Yichang City in Hubei Province in the east,with a total length of 193 kilometers.Numerous smooth rocky landslides are developed on both sides of the Yangtze River and its tributaries,which are large in size,with different deformation factors and damage types.Therefore,it is necessary to summarize and classify the deformation characteristics and effects of smooth rocky landslides in the reservoir area,as well as to objectively evaluate the damage of surge waves caused by instability,which has important scientific research value and practical significance.In this paper,on the basis of collecting information on the cascading rocky landslides in the Three Gorges reservoir area,we analyze the evolution of cascading rocky landslides,summarize their spatial and temporal distribution,external influencing factors and different sliding surface characteristics,and various types of deformation and damage modes represented,so as to construct a geological model of typical cascading rocky landslides-Muyubao landslides,and through the mining of accumulated displacement monitoring data,supplemented by numerical simulation Through the mining of accumulated displacement monitoring data,supplemented by numerical simulation,the analysis of the stability coefficient of the Muyubao landslide under different reservoir water level changes and 175 m water level surge hazard research mainly obtained the following conclusions.1.The formation of smooth rocky landslides in the Three Gorges reservoir area is divided into four processes:(1)transport and deposition of rock-forming materials;(2)absence and change of sedimentary phases during rock-forming process-formation of weak rock interlayer;(3)formation of geomorphology in the Three Gorges reservoir area under tectonic movement of the earth's crust;(4)continuous undercutting of the Yangtze River channel provides conditions for the development of smooth rocky landslides.2.27 smooth rocky landslides in the Three Gorges reservoir area,involving 20 counties and cities from Chongqing to Hubei,are mainly distributed in the main stream of the Yangtze River,with the south bank being the majority,while the tributaries are distributed in Zhuxi River in Wanzhou,Meixi River and Daxi River in Fengjie,and Qinggan River and Xiangxi River in Zigui.Spatial form: the height difference between the front and rear edge of these landslide points is in the range of 100-300 m,the water involvement rate is 20%-30%,and the slope of 20°-30° accounts for most of them,among which the height difference between the front and rear edge of landslide points in Zigui and Yunyang is relatively large;stability influencing factors: the formation of the head of the reservoir with the change of reservoir water level as the main external influencing factor,and the end of the reservoir with rainfall as the external influencing factor pattern.3.The sliding surface morphology of the 27 cascade landslides analyzed can be divided into six types: curved and straight,folded step,folded,circular arc,monoclinic straight and chair;the damage type is summarized into four ways: slip-shear type,slip-ultrusion type,creep-slip-slip type,slip-bending type.4.(1)From the overall analysis of the Muyubao landslide,the landslide deformation is concentrated in the right area;(2)From the analysis of individual monitoring points,the daily deformation rate of the monitoring point with the "diagonal" from the right border of the Muyubao landslide to the left front edge border is the largest,and the direction perpendicular to the "diagonal" is the(3)Analysis of the monitoring points from the horizontal and vertical profile lines of the Muyubao landslide:(1)When the Muyubao landslide is analyzed from the monitoring points of the horizontal profile line,the deformation of the monitoring points of the front edge of the landslide is the largest and the rear edge is the second largest;(2)When the Muyubao landslide is analyzed from the monitoring points of the vertical profile line,the deformation of the monitoring points on the left and right sides is large and the deformation of the monitoring points of the middle profile line is the smallest.5.(1)The dominant factor in the deformation of the Muyubao landslide is the high water level,and the longer the duration of the sustained high water level,the greater the deformation rate of the monitoring points,and the longest deformation lag time of the front and trailing edge monitoring points reaches 2 months;(2)The landslide deformation is more obvious in the stage of declining reservoir water level than in the stage of rising reservoir water level;(3)The deformation of the trailing edge monitoring points is synchronous with the rainfall relative to the rainfall,while there is a certain lag in the deformation of the monitoring points such as the leading edge.(4)The numerical simulation results show that:(1)the faster the reservoir level rises the greater the stability coefficient,and the faster the reservoir level falls the smaller the stability coefficient;(2)at the same reservoir level rise and fall rate,the stability coefficient reaches the extreme point with a time difference of 15 days,(3)under the continuous 175 m high water level operation the stability coefficient decreases continuously and eventually will be smaller than the stability coefficient of the initial 145 m water level,while in the reservoir level falls to 145 m and continues for a period of time,the stability coefficient starts to climb continuously.6.The initial sliding velocity of the Muyubao landslide is calculated to be 13m/s,the use of Surge numerical simulation of surge software for the Muyubao landslide river area of the surge calculation,according to the results obtained,divided into five levels of safety warning,and the landslide near the surge directly threatened by the area and the landslide body of residents and buildings Statistics were conducted,and the number of threatened people was calculated to be about 600 people and 177 houses. |
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