Experience gained until now underground mining worldwide and in Poland indicates that remnants may have an impact on the occurrence of seismic phenomena. Remnants are stress concentration sites encompassing both the deposit and the layers of rock mass located above and below the undisturbed rock. In the case where stresses in the remnant exceed its strength, it may collapse, and under unfavourable geomechanical conditions, stress-induced rockburst may occur. Remnants may also cause breaking of strong roof layers above their edges, which results in the occurrence of high-energy shocks (Salustowicz [30], Adach [3], Adach and Butra [4]).This article presents the possibility of utilizing numerical modeling to evaluate the influence of remnant upon the occurrence of seismic phenomena. The results of numerical calculations performed for a model room-and-pillar mining system with roof deflection under the conditions of copper ore mines in the Legnica-Głogów Copper District (LGOM) are presented. Numerical calculations in a plane strain state were performed by means of Phase2 v. 8.0 software for the analyzed mining system in which remnant was left behind. The results of numerical modeling showed that sudden fracturing of roof layers above the mined out space may occur on the edge of the remnant. This may cause a shock with very high energy, and under the appropriate conditions, this may lead to the rockburst phenomenon.

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This article presents the problem of seismic and rockburst hazard in underground hard rock mines. Types of rockbursts and their mechanisms as well as the causes of dynamic phenomena are discussed. The possibility of using numerical modeling to simulate the occurrence of a high-energy tremor, as a result of sudden shear rupture, is also shown. Results of numerical simulations are presented for a model mining field in a hard rock mine at high depth, in which the deposit is mined in a room-and-pillar mining system. General geological and mining conditions characteristic for Polish underground copper mines in Legnica-Glogow Copper Mining District belongs to KGHM Polska Miedz S.A. were adopted in the models. The typical lithological cross-section of the polish copper mines is characterized by rigid, high-strength rock layers in the roof, capable of accumulating elastic energy, while layers with much lower strength parameters are present in the floor. In the analyzed mining field, the remaining undisturbed rock, with a width of 40 m, was left. Numerical simulations were conducted in a plane strain state by means of Phase2 v. 8.0 software. An elastic-plastic model with softening was accepted for the rock mass. The results of numerical modeling showed that sudden (one computational step in the model) collapse of roof strata may occur over the excavated space on the edge of the remaining undisturbed rock, as a result of exceedance of shear strength, above all. This may cause a very high-energy tremor, and under the appropriate conditions, may result in the rockburst phenomenon.