The Stability Research Of Jiuzi Collapse Accumulation Wanjiakouzi Hydropower Station In Yunnan Province

Mountain has accounted for more than two thirds of the area in China, most of which is located in China's south-west and the Northwest Territories. In these areas, the accumulation bodies develop well, which form a large number of landslides, collapses. When construct here, such as the construction of the hydropower station, Cracking,disintegration and landslide will happen When is encountered in excavation or rainfall, which bring security risk to the builders and the progress of construction. Jiuzi collapse accumulation is located in the left bank of 400~1200 meters from wanjiakouzi hydropower station in the Xuanwei city Yunnan province. The accumulation is formed by large scale of collapse accumulation. Part of rocks are broken by collision and extrusion in the collapse and landslide progress, calcium re-cemented widespread after carrying surface water and groundwater components. Because the accumulation body is close from the dam, it is extremely important to study its stability.So, the stability of jiuzi collapse accumulation of wanjiakouzi hydropower station in Yunnan Province is studied in the article. Methods are used in equilibrium method(Morgenstern-Price method,standardize method) and strength reduction method, two profiles of A-A'and B-B'is studied of the collapse accumulation, the stability of the primary and secondary accumulations is analyzed and evaluated.Through the study of this article, the results are as follows:1. The primary and secondary accumulations of Jiuzi landslide are calculated by equilibrium method (Morgenstern-Price method,standardize method), the result of landslide Jiuzi is stable. We can draw the following conclusions by analysis of a variety of conditions:(1)The primary accumulation integral stability coefficient is higher than secondary accumulation, under the same conditions, secondary accumulation is easier to damage.(2)When considering water level drop and seismic factors, the stability coefficient of collapse accumulation will reduce, but the collapse accumulation is still stable.(3)Through the sensitivity analysis of water level drop rate between reservoir and groundwater, when the reservoir water decline slow, the stability of collapse accumulation is better, the fast reservoir water drop will make the stability of collapse accumulation drop significantly. Comparing the rate of groundwater level drop, a faster rate of groundwater drop is more conducive to the stability of slope.2. The stability of the collapse accumulation is calculated by strength reduction method, in which the stability coefficient is smaller than limit equilibrium method, but the collapse accumulation is still stable. The stability coefficient differs little or almost the same to different water level for the same collapse accumulation. The reasons may be subject to the limitations of the software and can not take full account of the factors on the stability of water impact.3. For the study area of the article, results calculated by strength method is different to limit equilibrium .For the reason, strength reduction method achieves limit equilibrium state by reducing material strength parameter, the same strength reduction for different soil materials means the same strength development for all kinds of soil. The stability factor and the sliding surfaces may be close to limit equilibrium method when using Strength reduction theory for homogeneous simple slopes, but there are large differences for non-homogeneous (eg. layered) soil. Comparing the maximum principal stress contour map in the reduction progress, we can see that the principal stress of the slope is changing in the continuous reduction of soil parameters, the stress of same point is increasing with the reduction of soil parameters, in other words, the stress field changes constantly. In other words,the stress field of slope has changed after strength reduction.4. As usual, the reduction of strength parameter of soil material can reduce other properties of the material. The strength parameters of a rock c and ? higher, the elastic modulus E higher, the Poisson's ratio lower. In the use of finite element method to search for stability factor, most of them are only for the strength parameters c and? , this article also adjust stiffness parameters E and v.