Research On Effect Of Increasing The Daily Drop Rate Of The Three Gorges Reservoir On The Stability Of Landslides In FengDu

The Three Gorges Reservoir is full of landslides, with the storage of the water, a large number of old landslides in the area produce different degree of deformation. When increasing the daily drop rate, it will have a bigger impact of the stability of the landslides, so it is necessary to carry out this research.Studying area is located in Chongqing, its about 434 km away from the Three Gorges Dam, the length of the reservoir is 49 km, the landslides are widely distributed in the study area, which poses a great threat to the life and property, which have 36 large representative landslides. Increasing the daily drop rate will destroy the original balance of the landslides, and will probably cause the landslides rise again. If we can increase the daily drop rate with the stability of landslides, it will improve the economic efficiency of the Three Gorges Reservoir and not cause the disaster. Therefore, researching on effect of increasing the daily drop rate of the three gorges reservoir level on the stability of landslides in Feng Du has important practical significance.In this paper, we use the landslides in Fengdu of the Three Gorges area as the studying objects, on the basis of fully analysis of the geological condition, and the landslide development characteristics om the area, we make a detailed research on the law of the landslides development, and classify the landslides, researching the influence factors of stability and deformation mechanism of the landslides. In the end, we use the qualitative evaluation and quantitative evaluation to analyze the stability of the landslides in the present situation,and the stability prediction is the condition of increasing daily drop rate. After the research we have the following results:(1) Location of the landslides in studying area are in the strata of J2 s, J3 s, and J3 p, the lithology is mainly sandstone and mudstone, they can be divided into three categories of engineering geological petrofabric: I, hard and thick layered sandstone; II, soft hard alternated layered sandstone and claystone interbedded; III to soft layered clay rock. The type of landslide deformation model are creep-crack, slip-crack, and slip-bending.(2) We counting the number of the landslides according to the engineering geological rock groups: there are 8 landslides in the Class ?, 13 in the Class ?, 15 in the Class ?. The landslides material composition are different when develop in different engineering geological rock group, we divided the material into 3 types: ?, large stone in the front area + Silty clay with fragments of stone in the middle and back area; ?, Silty clay with fragments of stone + sand rock stone cover on the slope surface in the front edge area; ?, silty clay, with fragments of mud rock stone.(3) The type of landslides are divided into 3 categories according to the action of the water:(1) hydrodynamic pressure type, there are 23 in the area;(2) uplifting weight loss type, there are 3 in the area;(3) composite type, there are 10 in the area.(4) Studying the influencing factors of landslide stability, and using Geo Studio software to numerical simulate the seepage characteristics with different factors, according to he simulation results and combine with example of deformation, we analyze the deformation development characteristics and mechanism in different type of landslides.(5) Establishing the qualitative evaluation method and quantitative evaluation method, for the hydrodynamic pressure type of landslides and composite ones which front height is lower than 159 m, we using the both method above to analyse the stability, for the landslides which front height is higher than 159 m, and for the uplifting weight loss type of landslides, we only use the qualitative evaluation method to analyse the stability.(6) We simulate and analysis the stability of Sha Tian landslide under present condition and increasing daily drop rate condition by using Geo Studio software, through analysis: in the process of reservoir water level descent, the balance of Sha Tian landslide was broken,causing seepage filed changed and stress redistribution, lead to the displacement concentrated area emerge near the fluctuating zone, in addition, because of raining, the slope of the rear part of the landslide also appears the displacement concentrated area, these two area will produce deformation and destruction, and the results are the same as investigation. But the deformation and failure appear in certain area, will not affect the overall stability of the landslide,so Sha Tian landslide will in the basic stability of the whole state in the present condition and increasing daily drop rate condition.(7) We found that by simulating other 35 landslides in the area, in current condition, there 27 landslides in the stability for the whole, 7 landslides in the basic stability for the whole, and due to the intense deformation in the front, there are 2 landslides in the basic stability for the whole and sub-stability of the front area. In the condition of increasing the daily drop rate, there are 14 landslides has weaked, statistics show that 15 in the stability for the whole, 18 in the basic stability for the whole, 2 in the basic stability for the whole and sub-stability of the front area, and 1 landslide in the basic stability for the whole and unstable of the front area...