Study On Classification Of Rock Mass Quality And Excavating Depth Of Available Foundation Of The Jinping Arterial Power Station

Based on the discuss of the engineering geological conditions of the Pusylog dam site of the Jinping arterial power station, The paper have found the main factors that affect the rock mass quality of dam foundation: lithology, rock mass structure, rock mass compactness, weathering, the properties of discontinuities and the effect of the deep crack, especially the deep crack is the particular thing other than the other power station. The paper then study on the classification of rock mass quality of dam foundation through the single factor classification and the multi-factors classification methods. The single factor classification includes lithology classification, weathering and stress release degree classification, rock mass structure classification, wave velocity classification etc. The multi-factors classification included the MZ (Modified Z System), the Rock Mass Rating (RMR) and the Rock Tunnelling Quality Index(Q) classification. The MZ system works through study the four main factors that affect the rock mass quality of dam foundation: the Strength of intact Rock material (Re), the Rock Quality Designation (RQD), the properties coefficient of discontinuities( the joint roughness number Jr/the joint alteration number Ja) and the intact index(Ky).Based on the classification results of the rock mass quality of dam foundation, the paper study in stress the relativity of the MZ values and the other classification results. The analysis results show that the MZ classification results are close to the field classification results, and are notable to the RMR system and the Q system classification results.As a part of the scientific research item of CHIDI that the study on the rock mass quality classification of dam foundation and corresponding mechanical property of the Jinping arterial power station, when have achieved above results, this paper provide the reference values of deformation modulus and shear strength of rock mass and discontinuities on basis of field testing data. The correlation analysis shows that the close correlativity of the MZ values and the mechanical parameters of rock mass, for example deform modes E0, so MZ classification is a very effective method.In order to lucubrate the mechanical character of the engineering rock mass of dam foundation, this paper pilot study the excavating depth of the available foundation through grading the rock mass quality of the II and II i section, meanwhile judge the availability of the rock mass of dam foundation according to the design criterion of the concrete arc damCSD145-85). In the end ofthis paper the planar finite element method is used to simulate the stress field and strain field of the slope of the II i section under deadweight before and after the dam foundation has been excavated. And then evaluates the possible destroy areas. The analysis shows the excavating depth of the available foundation is reasonable through grading the rock mass quality.