Study On The Influence Of Reservoir Water Level Fluctuation On The Seepage Field And Stability Of A Slope

In the southwest of China because of its special and complex geological conditions, resulting in the area to landslide, collapse is typical of the slope geological disaster extremely development, each year due to geological disasters caused casualties and economic losses bits are the highest in the first in the country. With the continued advance of China’s western development strategy and the Project of power transmission from west to east, under construction or proposed for water conservancy and hydropower engineering more and more in southwest of China. As one type of landslide, in addition to earthquakes and human factors, reservoir water level fluctuation is the main factor affecting its stability, and the stability of the reservoir is a direct impact on the normal operation of water conservancy and hydropower projects. Because of its special boundary conditions, material composition, deformation characteristics and the sensitivity of solid fluid coupling, Reservoir water level fluctuation affects the stability of the bank slope, which is easy to trigger large-scale slope geological disaster,. Reservoir water level fluctuation will change the groundwater level, the hydro geological condition and the physical and mechanical properties of rock and soil in the reservoir bank slope, and have great influence on the seepage field and stability of reservoir bank slope. Clarify the mechanism of large slope geological disaster triggered by fluctuation of reservoir water level, especially for the change law of seepage field and stability of the bank slope, has important theoretical and practical significance for the normal operation of water conservancy and hydroelectric power project and the geological disaster prevention and control.In this paper, the geological background of a planned hydropower station and the accumulation body of the dam is selected as the research object. Through the collection of relevant literature,to know that the power plant related survey and design units and scholars have been study deeply on slope toppling deformation body, and that only in conditions of reservoir water level fluctuation, toppling deformation body to maintain good stability. Therefore, in this paper, select the accumulation of the accumulation of ice water accumulation body as the main research object, and to study the law of change of the seepage field and stability under the conditions of reservoir water level fluctuation, and only to check the stability of the toppling deformation body.On the basis of detailed field investigation, studied the structure characteristics of the slope of rock and soil, the seepage field of ice accumulation body under the conditions of reservoir water level fluctuation is studied by physical simulation experiment and numerical simulation calculation in this paper, compared the analysis of physical model test and numerical simulation calculation results. The numerical simulation of the calculated groundwater saturation line substituted to stability calculation, calculated and checked stability of ice accumulation and toppling deformation body under the conditions of reservoir water level fluctuation respectively by improved transfer coefficient method and SLOPE / W, and analyzed and evaluation of stability. Through this study we obtained the following results:(1) The accumulation body in the study area is composed of two parts: the toppling deformation body and the ice water accumulation body. The study area developed a F1 fault which is almost parallel to the rock formation, and the small fault are the secondary production of F1. There are a number of extrusion surfaces and the collapse of the fracture section of the tunnel, in the first half of the body is more obvious. debris particle of ice water accumulation body is size to 10 ~ 200 cm, accounted for about 70 ~ 80%, more closely, no significant overhead phenomenon, density is middle dense to closely dense, and has a certain mud cementation at the bottom of bulk body.(2) The pore water pressure changes with the change of water level, the change of pore water pressure is positively correlated with the magnitude of the water level, and negatively correlated with the elevation of the measuring point. The higher the elevation, the change of pore water pressure which lags behind the changes in the water level is more evident.(3) although the value of numerical simulation and physical simulation is not exactly accordance, but the dynamic laws of the variation of pore water pressure under the conditions of reservoir water level fluctuation are both basically the accordance. The slope infiltration line changes with the change of water level, and lags behind the change of the water level, and more obvious.in the deep of the slope. In the suspension of impoundment or drain, slope infiltration line gradually gentle until to form a stable groundwater seepage field.(4) The evaluation of stability the slope:(1) the local and overall stability of the ice water accumulation body in the natural state before the water storage are both good.(2) When the water level rises to the normal level and the overall stability of the ice water accumulation body is good. When the water level raises, the stability coefficient decreases and then increases, and the stability coefficient changes little after the water is suspended.(3) When the water level dropped to the design dead water level, the overall stability of the ice accumulation body is good, the stability coefficient decreased and then increased under the condition of the water level drop,.(4) Local instability may occur in the reservoir water level variation range,The stability of toppling deformation body is good when it only under condition of reservoir water level fluctuation.In summary, the stability of the slope in the natural state is the best, stability coefficient of reservoir water level drawdown is less than the reservoir water level rise, the stability coefficient decreased about 8%, illustrated that influence on drawdown conditions slope stability is greater than the reservoir water level rise. Reservoir water level fluctuation has great influence on the stability of the ice water accumulation, but the influence of stability of the toppling deformation body is small.