One of the major shortcomings of two-dimensional approaches for underground excavation design is the (mostly) inadequate modelling of the effects of the face advance. Although they may roughly estimate the evolution of the displacements towards their final value, none of the 2D solutions provide information about the pre-relaxation the ground has undergone. The method presented in this paper represents an easy-to-implement tool allowing fast assessment of displacement development for a circular cavity in a Mohr-Coulomb material under hydrostatic loading. A numerical parametric study on a 3D model in FLAC3D (2006) has been performed. Based on the displacement data the respective fictitious support pressures have been back-calculated, using the closed-form solution developed by Feder & Arwanitakis (1976), thus allowing the establishment of three interpolation relationships. The knowledge of the shape parameters for an arbitrary set of mechanical parameters allows the calculation of the displacement path. The results have been verified on a set of ten 3D calculations and the presented method is demonstrated through case histories.

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