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The swelling phenomenon in tunneling is numerically modelled as a coupled hydraulic-mechanical process. The present communication focuses on the significance of the seepage equations. We consider the rock mass conceptually as a porous medium with natural or excavation-induced fractures. The rock mass permeability is governed by the fractures, provided that they are saturated. With increasing pore water suction, the fractures desaturate. Accordingly, we idealize the rock mass as a porous continuum with a permeability which depends on the pore water pressure. The observed absence of swelling deformations at the tunnel walls and the crown can be explained as a consequence of varying hydraulic boundary conditions along the excavation boundary. According to our numerical results, the nonlinearity of the seepage equations has a decisive qualitative influence on the model behavior, and it enables realistic modelling of the observed deformations, i.e. solely at the tunnel floor.
Index Terms:rock; TunnelingGroup
Further Information:Date published: 1992