Research On Safety Of High Rockfill Cofferdam For Large Hydropower Station

Cofferdam is an important temporary structure in the hydro-junction engineering construction.It affects the safety and the schedule of the entire construction,and the safety of the downstream. Along with the constructing of large or even giant hydro-junction, cofferdam has likewise enlarged the scale and has become difficult to build .This thesis takes Wudongde hydroelectric power station upstream high rockfill cofferdam as the object to study,and carries out the research on seepage and stability of slope. The prime tasks are as follows:1)The basic principles and methods of seepage analysis and slope stability analysis are introduced, and different methods are compared. The seepage continuous equation is derived from the law of mass conservation and the two-dimensionally nonstable-nonsaturated seepage finite element dominative equation is deduced from variational principle.2)The impact of the seepage coefficient varied from area on the seepage, the impact of the nonstable-nonsaturated seepage on the slope stability,and the method of choosing intension parameter for coarse soil are discussed ,and some conclusions are proposed.3)The seepage characteristic under different operating modes of Wudongde upstream cofferdam are computed. The sensitive analysis of seepage parameter and velocity of pumping water of the foundation ditch are carried out. The leakage and the seepage stability are evaluated.4)On the basis of the seepage analysis, non-linear intensity criterion and the limit equilibrium method are used to compute the stability of the slope .The sensitive analysis of the seepage parameter of the deep and thick overburden and the soil shear strength are carried out. The impacts of the non-saturated problem on the stability of the slope are also analysed.