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An analytical solution is presented for the time-dependent stresses and displacements around a circular hole when it is loaded by an axisymmetric internal and far-field pressure. The material is assumed to be elasto-viscoplastic with dilatant plastic deformations according to a non-associated flow rule. Strain softening is considered by a modified St. Venant slider which is characterized by MohrCoulomb yield conditions for both the peak and the residual strengths.
Index Terms:tunnel; rotational symmetry; analytical; rock; TunnelingGroup; rheology; analysis
It may be shown that for the elasto-viscoplastic material model presented, an optimum time of installation for the lining does not exist. This is because for an infinitely small, but positive internal pressure, numerically a stable equilibrium will be reached, even without a lining. The introduction of such a small, fictitious internal pressure for numerical reasons only seems always to be justified. Disregarding big deformations, stability will therefore, theoretically, always be guaranteed.
Further Information:Date published: 1984