| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程系 === 94 === The research utilized a three-dimension discrete element code, 3DEC, which is suitable for simulating the discontinuous rock mass, to study the stress transmissions and the deformation behavior of tunnels excavating towards the discontinuous geological interface by elasto-plastic analysis. The conditions of different geological index and in-situ stress were considered. The plots of influence lines, trend lines, and displacement vector orientation trend lines were used to predict the geological conditions in front of the excavation face. Differences in the mechanical behavior for tunnels with or without supports were compared.
Based on the results of numerical analyses, several conclusions can be obtained. (1) The ranges of plastic zones for discontinuous interface are larger than for continuous interface. (2) Under the condition of discontinuous interface, no matter the tunnel is excavating from stiff rock to soft rock or vice versus, stress would concentrate around the corners of the excavation face and would become more obvious as the excavation approaching the interface. (3) The discontinuous interface will have obvious influence on the stress transmissions and the deformation behavior of tunnels. Therefore, it will result in different characteristics of the trend lines of the displacement vector orientation when the tunnel is excavated towards different geologic conditions. (4) The installation of tunnel supports can restrain tunnel deformations effectively; therefore, the normal values of the trend lines of the displacement vector orientation will decrease substantially for both stiff and soft rock. (5) Under the condition of discontinuous interface, the width of the weak zone in front of the excavation face has little effect on the trend lines of the displacement vector orientation.
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