: In this paper, the estimation of boundary conditions for rock mass models is addressed by means of Bayesian identification procedures. Basic information can consist of stress, strain, or displacement measurements. Previous information is accounted for, so that boundary conditions can be updated at the various stages of a project, as soon as new information becomes available. For linearly elastic rock masses, the boundary conditions are computed in a one-step solution. For rock masses with non-linear behavior, an iterative procedure must be followed. The proposed procedure was applied to two- and three-dimensional non-linear models of the Underground Research Laboratory (URL) of the Atomic Energy of Canada Limited (AECL), Canada. The 3-D model was able to completely reproduce the complex stress pattern measured in situ, and the 90 ° rotation of the principal in situ stresses with depth. In order to reliably estimate the boundary conditions reproducing the current in situ state of stress, response measurements of the rock mass to current disturbances are necessary as input data.
Any rock mechanics study starts with the determination of the force fields in which the rock mass under study is embedded. Body forces and boundary conditions determine these force fields. The latter fields may be very complex, due to local variations in rock mass structure (petrography, discontinuities, heterogeneities, folds, faults, dikes, fabric, etc.), or to major structural features, such as faults at the regional scale. Faults may define stress domains at a large scale and cause rotations of principal stress directions.