The Garpenberg mine, owned and operated by Boliden Mineral, has conducted tests of rill mining in the Dammsjön orebody to increase production. Dammsjön is a steeply dipping orebody surrounded by limestone on the hangingwall side and a quartzitic rock on the footwall side. The rill mining test was conducted on the 753 meters level and had a bench height of approximately 10 meters. Monitoring data obtained during the rill mining provided an opportunity to create a numerical model representing the real rock mass. The model could be calibrated to replicate the behavior observed in the monitoring data. As a first part of this thesis work, analyzes of the monitoring data showed that the problem could be considered two-dimensional (2D).A 2D model was created in the numerical code FLAC. The model was calibrated, in terms of material parameters of the rock mass and mechanical parameters of the contact zones between them, to replicate the rock mass behavior observed in the real rock mass. The desired behavior included (i) deformational pattern, (ii) magnitudes of deformations and (iii) relationships between the magnitudes of roof and wall deformations. A three-dimensional (3D) model was also created in the numerical code FLAC3D. The model is an extension of the 2D model in the third dimension and represents the real test mining sequence. The 3D model was used to verify the behavior of the rock mass in three dimensions. The 3D model also includes ground support in terms of rock bolts installed in the drifts in the same manner as in the real mining operation. In future work, the bolted 3D model may be calibrated against the observed bolt failures of the test mining to further increase the reliability of the model.Two sets of material parameters were determined that made the model replicate the desired behavior. The calibrated 2D model was finally used to investigate alternative geometrical cases of rill mining that the mine expects to encounter in future mining. The investigation included ore widths of 8, 12 and 16 meters with bench heights of 10, 12 and 15 meters, respectively. Analyzes were also conducted regarding four consecutive levels of rill mining with the same nine geometric cases as above. The investigations included analyzes of deformation, stress redistribution, yielding, and sliding along the ore – host rock contacts. The mine strives for failed rill benches before extraction in terms of destressing, but without collapse.The recommended bench heights for conducting rill mining under the conditions of this study are: (i) for 8 meters wide orebodies, bench heights of 10 meters or lower are required to ensure failed benches before excavation, and (ii) for 12 and 16 meters wide orebodies, bench heights of 15 meters are possible, while still having failed benches to extract.The analyzes of alternative mining geometries showed that roof displacement increased with increased bench height, but decreased with increased ore width, wall displacement increased with increased bench height, but decreased with increased ore width and sliding along the ore – host rock contacts increased with increased bench height, but decreased with increased ore width.Keywords: Boliden Mineral, Garpenberg, rill mining, FLAC, FLAC3D, numerical modeling, calibration, stability, deformation.