Study On Rock-mass Structure Characteristics And Slope Stability Of Highway In The Metamorphic Rock Qinling Orogenic Belt

Qinling Mountains is a typical place where metamorphic rocks are widely distributed. The special nature of the metamorphic rocks has affected the stability of the slope and restricted the construction and safe operations of highway. Analyzing the main control factors of slopes in the metamorphic rocks area, identifying the rock deformation and failure mechanism, and possible failure mode, and presenting the evaluation method of the stability have important theoretical significance and practical value for reasonable slope designing and treatment programs, and effective prevention of geological disasters in the slopes. In this thesis, regarding rock structure research of highway slope in Qinling metamorphic rocks as the starting point, with the main line of geotectonics, metamorphic petrology and rock structure theory, the author analyzed systematically development features of metamorphic rocks structure, mechanical properties and failure mechanisms of metamorphic rocks, deformation and failure model of metamorphic rocks and the stability of slopes by using the methods of the site geological survey, laboratory testing, theoretical analysis and numerical simulation.The main research results are as follows:(1) The author studied sedimentary formation, deformation—deterioration and post-transformation of metamorphic rocks mass in the Qinling orogenic belt with geotectonics, proposed controlling system of metamorphic rocks mass to Qinling geosyncline and found that inland orogeny is the important process of rock mass deformation and the basic form of controlling rock mass structure, which laid a foundation for the further research on rock mass structure characteristics of metamorphic rocks slope.(2) The author studied characteristics of metamorphic rocks in Qinling with metamorphic petrology and rock and mineral identification. Metamorphic rocks in Qinling are divided into four categories of twelve sub-types of rock group by lithofacies, structure and basic mechanical properties through investigations.(3) On the basis of site geological survey, from the significance of the rockmass structure and engineering geology, metamorphic rock mass structure is divided into five levels by the scale of region. Also, the author made a detailed study of level III and IV structure features which has a direct controlling influence to the stability of slope, and thought that the structural distribution and occurrence is the important influence factor of metamorphic rock slope structure.(4) Based on the research of the discontinuity and structural body, rock mass structure of metamorphic rock slope is divided into four categories of nine sub-types, in which the most common are layered structure and loose structure, according to the characteristics of metamorphic rock slope.(5)The thesis made a systematic tests study on physical and mechanical properties of mylonitize phyllite developed in Qinling metamorphic rocks zone for the first time and got the complete stress-strain curve. Also, the author analyzed the types and mechanism of rock deformation and failure, and obtained deformation and mechanical parameters of mylonitize phyllite. It is showed that rock microstructure formed metamorphism has significant influence on the mechanical properties of the metamorphic rocks, the discrete test results, and the widely different between mechanical properties parallel to foliation and perpendicular to foliation.(6) The author summarized the distribution and influence factors on deformation and failure of highway slope in metamorphic rocks. Through a large number of survey and analysis of the slope in Qinling, a systemic deformation and failure model of metamorphic rock is proposed, based on a detailed analysis of the influence factors on slope deformation and failure, combining rock mass structure characteristics of highway slope in metamorphic rocks, slope structure, rock association and weathering features.(7) After a systematic summary of lithology, rock structure, slope angle, and the failure mode etc. in the slope, a comprehensive evaluation standard is proposed. Taking the stability analysis on typical highway slope in metamorphic rocks for example, the author puts forward technical strategy and methodological system on the stability analysis and calculation of highway slope in metamorphic rocks by using the methods of structural analysis, quantitative evaluation and stress-strain analysis.