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The article presents the suitability of the new measurement techniques for monitoring deformations of the technological pillars and fragments of the face in underground mining. The conducted observations concerned the mined pillar located in the lead of mining field G-3/4 of Rudna mine (mine belongs to KGHM Polska Miedź S.A.) in a situation of constant progress of mining works in its direction.The observations conducted underground provided results demonstrating the suitability of the applied observation techniques in this area. The obtained measurement data directly describe the volumetric changes which form the basis for assessing the stress of the rock formation. This issue is well recognised based on the tests on rock samples. Further studies should concern the transfer of these experiences to the results of in situ observations.

Abstract. The copper ore deposit of the Legnica-Głogów Copper Mining District a one-deck bed formed from the contact of weak sandstone rocks, and solid, durable dolomite rocks, separated by a layer of copper slate. The bed operation is carried out using the room and pillar system. The course of deformation in such bed operation systems is determined by the mutual interaction of particular elements of the geo-mechanical system which include: the roof slab, the pillars and the excavation bed. Due to the possibility of human intervention, structural pillars -whose strength properties can be determined by the appropriate selection of their dimensions and shape -play a particular role in this system. The optimization of the properties of these pillars is mainly based on the results of laboratory tests of rock samples in the strength test machine and on the basis of visual observations of their behavior in situ. The article presents the experimental results carried out under pit conditions in order to determine the rock pillar reaction. Suitable observations were made using the so-called volumetric method. The obtained results were discussed in relation to the results of strength tests on rock samples, indicating the limited similarity to the deformation characteristics.