A-BQ, a classification system for anisotropic rock mass based on China National Standard
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A-BQ, a classification system for anisotropic rock mass based on China National Standard GUO Song-feng(郭松峰)1, 2, 3, QI Sheng-wen(祁生文)1, 2, 3, SAROGLOU Charalampos1, 4 1. Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 2. Innovation Academy of Earth Science, Chinese Academy of Sciences, Beijing 100029, China; 3. University of Chinese Academy of Sciences, Beijing 100049, China; 4. School of Civil Engineering, National Technical University of Athens, Athens, Greece © Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract: The rock mass in nature is in most cases anisotropic, while the existing classifications are mostly developed with the assumption of isotropic conditions that not always meet the engineering requirements. In this study, an anisotropic system based on China National Standard of BQ, named as A-BQ, is developed to address the classification of anisotropic rock mass incorporating the anisotropy degree as well as the quality of rock mass. Two series of basic rating factors are incorporated including inherent anisotropy and structure anisotropy. The anisotropy degree of rock mass is characterized by the ratio of maximum to minimum quality score and adjusted by the confining stress. The quality score of rock mass is determined by the key factors of anisotropic structure occurrence and the correction factors of stress state and groundwater condition. The quality of rock mass is characterized by a quality score and classified in five grades. The assessment of stability status and probable failure modes are also suggested for tunnel and slope engineering for different quality grades. Finally, two cases of tunnel and slope are presented to illustrate the application of the developed classification system into the rock masses under varied stress state. Key words: anisotropy; rock mass; basic quality; classification; tunnel; slope Cite this article as: GUO Song-feng, QI Sheng-wen, SAROGLOU Charalampos. A-BQ, a classification system for anisotropic rock mass based on China National Standard [J]. Journal of Central South University, 2020, 27(10): 3090−3102. DOI: https://doi.org/10.1007/s11771-020-4531-7.
1 Introduction As valuable and acceptable tools for engineers, a number of rock mass classification systems have been developed for the past decades starting from TERGAZHI [1]. Nowadays, the classification approach serves as indispensable basis during the design and construction of complex excavations in rock masses. The rock mass classification system Foundation
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should incorporate three factors generally. Firstly, the properties of rock matrix, e.g., strength and deformation of intact rocks, make a basic contribution to the ratings. Secondly, the features of rock mass structure, e.g., the density, orientation and surface condition of discontinuities, play a dominant role on the rock mass quality. Finally, the geological circumstances of rock masses, e.g., geostress and gro
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