| Sanhekou hydroproject hub is one of the two sources of the Hanjiang-to-Weihe RiverWater Transfer Project and is the regulation and storage hub of the water transfer project.The concrete arch dam is selected as the river dam initially, and the maximum height of thedam is145m. The bedrock in dam area are mainly the metamorphosed sandstone andcrystalline limestone of the metamorphosed sandstones in the lower silurian meiziya group,and the dam valley shows symmetrical "V" shape. The arch dam has a greater advantagethan other types of dam in terms of safety and economy, but it also has a more demandingrequirements in the choice of the foundation surface. It needs to make a detailedidentification on the engineering geological characteristics of the dam and abutment,further research the weathering characteristics, rock mass structure, rock mass qualitygrading and other, and accurately obtain the physical and mechanical parameters of rockmass. Then we can evaluate and grad the rock mass quality reasonably, which provides animportant basis for the selection of foundation surface and the design of arch dam. Theprevious research results of the foundation rock mass home and abroad cannot be directlyapplicable to research the foundation rock mass of Sanhekou reservoir, therefore we mustestablish a unique research program based on the characteristics of the foundation rockmass of Sanhekou reservoir. The main contents in this study are as follows:(1)Based on the analysis of the relationship between the longitudinal wave velocity andthe depth of the adit rock mass, combined velocity ratio, completeness coefficient and otherquantitative indicators and according to the existing norms and the adit field survey data,the author divided the weathering degree of the abutment and foundation rock mass anddetermined the thickness of the rock mass with different weathering degree.(2)Based on the analysis of the development characteristics, spacing change with theadit depth, grading and the filling state of structural plane, using structural plane spacing,completeness coefficient, RQD and other quantitative indicators, combined with thehydraulic and electric engineering geological investigation, the author created the structureclassification criteria and made a structural classification for the rock mass in Sanhekoureservoir arch dam area, and then carried out a comparison in three dam line. (3)Based on the comprehensive analysis of the engineering geological characteristicsof the rock mass in Sanhekou reservoir dam area, the author selected representation targets,such as deformation modulus, longitudinal wave velocity, completeness coefficient, rockshear strength index and type of rock mass structure,to establish the quality grading criteriafor the rock mass in the Sanhekou reservoir dam area, and made a qualityclassification,using the BQ grading standards, the hydraulic and electric engineeringgeological investigation and the grading standards established in this paper, finally,determined the rock mass quality classification by comparative analysis comprehensively.(4)According to the analysis of the high arch dam requirements for the mechanicalproperties, such as bearing capacity, deformation capacity and shear strength of the rockmass and after the analysis of the selection factor in the foundation surface of the Sanhekoureservoir arch dam and selecting a representative indicators, the author uses multiarch-cantilever method to analyze the arch spandrels stress of the Sanhekou reservoir archdam, and established the quantization criteria to select the foundation surface of theSanhekou reservoir arch dam and determined the foundation surface for the dam foundationand abutment based on the comprehensive analysis of the stress. |
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