In this paper, 3D HM computations are performed to predict the rock response during the excavation of a new gallery (mine-by test) realized in Opalinus clay at the Mont- Terri laboratory, Switzerland. In a first part, previous mine-by tests in similar materials are reviewed: the CLIPEX experiment in Mol (Belgium, Boom clay), the MODEX-REP experiment in Meuse Haute Marne laboratory (France, Callovo-Oxfordian Clay) and the ED-B at Mont Terri (Switzerland, Opalinus Clay). Possible relevant processes are identified. Secondly, the hydro-mechanical formulation used to reproduce the test is described. Thirdly, a 3D HM model adapted to the investigated mine-by test is set up. This model accounts for the anisotropy of the initial stress state and hydro-mechanical material properties (stiffness and permeability). Finally, the influence of anisotropy of stress state and stiffness are investigated by means of a sensitivity analysis.