Study Of Genetic Mechanism About Dolomite Sandification In The Site Area Of Pingtou Hydroelectric Station Of Meigu River And Its Influence On The Project

Nowadays, in the construction of water conservancy and hydropower of China's karst developing area, there are still many difficult problems to be a better solution. Along with each kind of engineering construction's rapidly expanding in the Karst developing area, the question which meets can also be more and more, and be more and more complex.In Pingtou Hydroelectric Station of Meigu river, 5# Branch Cave control section of Diversion of main hole, the surge tank upper chamber transportation hole, the butterfly valve chamber transportation hole and the pressure piping even section construction hole has indicated, in the research area, the fine crystal dolomite and middle crystal dolomite in vertical depth of 200-240m, and the horizontal depth of the 110m place, the Karst process to be intense. The surrounding rock assumed sand of granular structure to clamp the dolomite rubble stone, called it "dolomite sandification". The research area of dolomite sandification has tremendous influence to the construction of Pingtou Hydroelectric Station, which causes the factory site area various hydraulic engineering structure construction progress to be slow, increases the project construction cost greatly and threatens seriously constructors' lives. Moreover, it is essential to stability evaluation of surrounding rock and the whole bank slope after the Hydroelectric Station operates. Therefore, it is important for people to research mechanism of dolomite sandification and the influence to project in the site area of Pingtou Hydroelectric Station.The research results may carry on the instruction directly to the construction, and provide scientific basis for prediction of the development of dolomite sandification in Pingtou Hydroelectric Station. The exploration, construction information and data of Pingtou Hydroelectric Station have been investigated and analysed. In view of "dolomite sandification" this special geological phenomenon, using the prototype investigation and the indoor analysis to unify, the macroscopic analysis and the microscopic analysis to unify, the scene test and the laboratory test to unify, the pattern analysis and the simulator study to unify, the analytic hierarchy process and the systems assessment to unify, the paper has analyzed the special mode between dolomite sandification and surrounding factor (including lithologic association, geological structure condition, underground hydrodynamic conditions of groundwater, hydrochemistry condition and so on). It evolves historical and development gradualness along with the time development. The form, the evolution and the present situation are grasped from the process and in the internal action mechanism. The research results not only have solved the project actual problem, but also make progress in the research aspect of "dolomite sandification".The following questions are mainly discussed in this paper:①The landform and physiognomy, formation lithology, geological structure, hydrogeology, local tectonic stability assessment, physical geological appearance and other engineering geological condition are analysed and researched. The engineering geological condition of research area is evaluated.②The structural characteristics of dolomite sandification in the research area is concluded, including the structural characteristics of dolomite which is sandificatd and the structural characteristics of sandification along with rock fracture. By doing chemical total analysis test with dolomite and dolomite sand, geochemical characteristics of dolomite sandification is systematically described.③Spatial distribution characteristics of dolomite sandification in the research area is inducted. Macroscopic mechanism of dolomite sandification is deeply studied. The effect of dolomite sandification to lithologic association, geological structure condition, hydrodynamic conditions of groundwater, hydrochemistry condition and so on is systematically analysed.④By doing thin section identification test and scanning electron microscope test, microtexture and microstructure of dolomite in the research area is analysed. By investigating microscopic dissolution characteristics of dolomite, microscopic mechanism of dolomite sandification is described.⑤By investigating genetic mechanism of dolomite from macroscopy to microcopy, law of formation and evolution of dolomite sandification is deeply investigated. Moreover, development regularity of sandification in the research area is put forward.⑥On the base of analysis and research above, the effect of hillside stability which comes from dolomite sandification in the research area is evaluated by using geological analytical method in this paper.