| Ciha Gorge hydropower station locates on the border of Xinghai county and Tongde county,Qinghai province. It is a comprehensive water conservancy and hydropower project which takes power generation as primary, combining with lood-prevention and sand-blocking functions. The power station is initially designed with 250 m dam height and 1800~2000MW installed capacity. The abutment slope vertical heights difference of Ciha Gorge hydropower station is about 400 m. Besides, the whole gorge slope is steep and nature slope general exceeds 40 degrees, even go beyond 60 degrees in some regions due to the stream trenching. It makes the slope which located behind the right bank dam of Ciha Gorge hydropower station reach a height of 440 m and a gradient above 50 degrees. As a result, the slope stability becomes a crucial issue on the safe operation of the power station. The complicated geological structure brought greater difficulties to the research on slope stability. On the basis of detailed investigations and precision measurements at the scene, and indoor and outdoor tests, the author deployed a research on the boundary conditions, slope rock mass mechanics parameters and the stability of the slope located behind the right bank dam of Ciha Gorge hydropower station. This paper detailed introduces slope engineering geology environmental condition of the Ciha Gorge hydropower station, and the study on forming mechanism and space distributing character of the intake slope tilting body and slope characteristics of rock mass structures and mechanical property. Also the paper adopts field qualitative analysis method to studying slope rock mass quality. The main results are listed as followings:(1) Based on detailed measurement data from total station, we acquired the distribution characteristics, distribution proportion of lithology as well as spatial distribution characteristic of each lithology, and established 3D model. By the cutting of the 3D model, we obtained the distribution and combination of each dam profile, which laid the foundation for subsequent analysis and calculation.(2) The structural surfaces in dam site were measured accurately, specifically rigid structural planes developed in each position were measured in a large area; More accurately grouping feature of dominant direction were obtained after statistics analysis. The development of the weak structural planes and faults are investigated layer by layer and a 3D model was built. With the 3D model, we accurately located the weak layer in various parts of the slope which may form boundary conditions.(3) Through the investigation and statistics analysis, the type of rock structure and the slope body structure of the slope located behind right bank dam was obtained according to the related standards.(4) According to the results which were accurately measured on the scene and preliminary exploration data, the depth of the rock mass’ s weathering and unloading were divided.(5) Different boundary conditions which may make the whole slope damaged were investigated, and the mechanism was analyzed based on the analysis of the deformation and failure characteristics of slope..(6) Combining with the engineering characteristics of rock mass itself, longitudinal wave velocity Vp value estimation formula based on experience and fine measurements and tests, we gave a comprehensive classification on the rock mass of slope quality. It further provides a new way for more rapid, accurate evaluation method of rock mass quality.(7) With a number of indoor and outdoor tests, the studies about mechanics parameter selection were taken, and we obtained the rock physical mechanics parameter of every single rock mass and fault gouge on boundary controlling region. |
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