Study About The Deformation Properties Of The Columnar Joints Basalts For The Foundation Of The High Arch Dam Of Baihetan Hydropower Station Jinsha River

Arch-dam is one of the dam that is reasonable economy, safety and reliability, but the stability of the arch dam is mainly relying on the rock mass of the cross-strait abutment to maintain. One of the most common form of the instability of abutment rock mass is the slide damageof the rock mass by loading, and the other is the occurrence of an extensive yield or excessive inhomogeneous deformation of the rock mass by loading. As a special shell structure, arch dam is very sensitive to the deformation of dam foundation(abutment) rock mass, and in particular the inhomogeneous deformation of the dam will lead displacement of stress or stress concentration, then impact the overall safety of dam. But because of the existence of the columnar joints of basalt that the deformation modulus is relatively small and to be easy to produce inhomogeneous deformation in the left abutment of Baihetan Hydropower Station, becomes one of the important engineering geology problems to the Hydropower Station. Based on the research of the rock mass structure of the basalt and the division of rock mass quality, especially the spatial distribution, structural characteristics, strength and deformation characteristics of the columnar joints of basalt, with the numerical simulation, it proves the feasibility that the columnar joints basalt used as the foundation. mainly achieves the following results:(1) Baihetan Hydropower Station mainly develops intrastratal faults and interlayer faults, faults, basal joints and the columnar joints, which, intrastratal and interlayer faults and faults mainly control the macro-structure of rock mass, and the joints impact the local structure and integrity of the rock mass. On this basis, by a great deal of information statistics and some experiences of other engineerings, we put forward the division standard of the rock mass structure. From the classification results, the rock mass structure of right bank is_generally superiors to the left bank's. In addition, according to the basic principles for the rock engineering geology of of classification in "Water Resources and Hydropower Engineering Geological Survey standard GB50287-99", aiming at the high arch dam about the size and structure, we put forward the classification scheme of the rock mass quality for Baihetan Hydropower Station. Results from the classification, from lower elevation to higher elevation, the rock mass quality gradually deteriorate, and the rock mass quality of right bank is better than left bank's overall.(2) Based on the analysis for the characteristics of the spatial distribution of the columnar joint basalt, it introduces its rock mass structure characteristics from the geometric features, development characteristics of structural face and so on. And then comparatively studies the differences of the strength and deformation characteristics between the columnar joint basalt and general basalt, the results showed that both the the value of strength and deformation modulus become low, and the latter relatively lower.(3) By establishing the 3-D finite element model of Baihetan Hydropower Station, it has an analysis and study the stress, displacement and deformation and damage the region in detail for the rock mass of dam foundation and the arch dam. The results show that, under the influence of columnar joints, the displacement of rock mass of dam foundation and the arch dam both increase , and the area of distribution range for plastic zone become enlarged. But simulation results showed that arch dam under the influence of columnar joints has not appeared the displacement of stress or stress concentration obviously, and it is not enough to be a real threat for the arch dam.However, due to the existence of columnar joints, plastic and displacement increases, it is adverse to the long-term security for project operator, and needing the necessary reinforcement.