Ground Response to Tunnel Re-profiling Under Heavily Squeezing Conditions

This paper presents a finite strain theoretical analysis of the ground response around highly deformed circular tunnel cross sections that are subjected to (repeated) re-profiling in order to re-establish the desired clearance. Plane strain axially symmetric conditions are considered, with linearly elastic, perfectly or brittle plastic rock behaviour according to the non-associated Mohr-Coulomb model. On the basis of this theoretical analysis, some practical questions are addressed with respect to the ground response curve, the maximum rock pressure (as carried by a practically rigid new temporary support) and the maximum wall convergence (as expected in the presence of a light new support) after re-profiling. Finally, the paper revisits the question of the effectiveness of a pilot tunnel with respect to the ground response during enlargement of the tunnel cross section.