Sedimentary rocks with layered structure account for two third of global land area, and this proportion is 77.3% in China, lots of metamorphic rocks also have significant features of layered structure, so there are a large number of stability problems about layered rock mass in mining engineering. Layered rock mass is generally considered to be transversely isotropic solid in mechanics. Based on the complex variable expression of displacement components of transversely isotropy, the displacement analytical solution of a deep elliptical tunnel in transversely isotropic rock mass is derived by conformal mapping method.
In order to study the stability of layered rock mass, a shear failure criterion for layered rock mass is presented and its program is compiled in C language. The shear failure criterion consists of two parts: firstly, four empirical expressions are suggested in which shear strength parameters vary with the direction; secondly, a pilot calculation method is developed to judge whether a shear failure plane in layered rock mass occurs or not and give its occurrence under three dimensional stress condition. A triaxial numerical experiment on layered rock mass is designed to test the shear failure criterion, and its results reflect the characters including obliquity effect, confining pressure effect and failure mode which conform to the previous triaxial tests.
In order to study the influence on the different parts of the cavern by joints, the three-dimensional model is built by Patran and then calculated with FLAC3D after meshing. Seven working conditions about different inclination of joints (0°15°30°45°60°75°90°) are considered in the calculation. The results show that low dip joints in vault and steep joints in the sidewall are more dangerous. Therefore, some measures should be used when encountered this situation in this project.
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