Landslide Stability Qualitative Analysis And Quantitative Calculation-Landslide Effects On The Selection Of Site For Yangqu Hydropower Station

As the economy develops,in order to accelerate the cascade development of hydropower projects in the upper reaches of Yellow River and meet the growing power demand of Yushu and Guoluo autonomous prefectures of Qinghai Province,as well as considering the engineering construction demand of South-to-North Water Diversion Project,the geological problems in choosing dam site of cascade hydropower stations must be studied.There are some exploration results such as borehole data and footrill data about the upper stream dam site,and several severe geological problems such as landslide and loose deformation in both sides of this dam site are found.Using geological mapping,borehole survey,test pitting,costeaning,geophysics prospecting,comprehensively explored and studied the geological conditions of the midstream dam site and downstream dam site,and calculated the stability of the sliding mass.Major work of this dissertation:(1)The research contents of this dissertation are the appearance characteristic of sliding,the structure characteristic and deformation&fracture characteristic of the sliding mass.The deformation&fracture characteristic of this sliding mass is very clear:it has a very steep front,the gully erosion is very intensive,the slide fracture in shallow part and surface is quite obvious,the main scarp in rear part is very clear,there are tensile fissures in part of this sliding mass.The creep sliding-tension cracking characteristic is very obvious.(2)The mechanism of landslide and its formation condition,and the stability estimation of sliding mass.In this dissertation,the finite element method and unbalanced thrust transmission method are used here for stability estimation.The contents include the determination of computation method,the computation and analysis of sliding mass stability before and ajfter water impounding.(3)The computation and analysis of the sliding speed of sliding mass.Since the landslide is located near the midstream and downstream dam site,once it loses its stability,the safety of the dam will be threatened.To estimate the effect of the landslide instability to the downstream dam,the slide speed is calculated.In this calculation,Panjiazheng method and energy method is used to calculate the longitudinal section,and the border of the landslide in each section is determined by geological block borders.Let storage water level be 2715,take real project condition into calculation.(4)Landslide swell calculation.Once landslide occur and massive rock and soil rush into reservoir with great speed,swells will be generated and threaten the reservoir dam.According to the swell speed calculation result,three methods are used to estimate the height of the swell.Considering the characteristic of the lower reach of this river,suggest that in normal storage water level condition,the swell height before the midstream dam is less than 2.5m,and the swell height before the downstream dam is less than lm.(5)Basic characteristics of the deformed landslide.The mechanism of landslide deformation.Calculation about the landslide uses force transfer coefficient method which is also a finite element method.There are landslide and deformed body rock at the left bank of the upstream dam site.In natural condition they are temporarily stable,but when the water reservoir is full of water,they may lose stability and causes disaster.