Abstract

The main objective of the presented analyses is to find the bridge between the solutions of the geomechanical and related geophysical problems addressed to the selected archival seismic events. This permitted finding such geomechanical formulae, involving components of rock mass' strain/stress states and the material characteristics, which on the basis of the long-term path of rock mass loading due to mining predicted by numerical modeling, could indicate the necessary conditions which should be fulfilled if the anticipated by methods of geophysics failure mechanism could develop.

1 Introduction

The Legnica-Głogów Copper Basin is the area where the underground copper mining operations are usually associated with a high seismic activity. For better understanding of this type of seismicity, the stronger tremors' focal mechanisms are investigated on the routine bases in the local mines' seismic stations. These investigations permit recognizing stress-deformation processes which occur during a given tremor's occurrence.

The largest risk for the mining operations are created by high-energy tremors which hypocenters are located within the main roof strata, about 40–200m above the excavated copper ore body. The most often encountered focal mechanisms of the such tremors are the slipping type mechanism with the rupture plane which spatial location is frequently correlated with tectonic structures located nearby. However, seismic tremors in Polish copper mines occur equally often in the areas which are virtually free of tectonic disturbances. Therefore one may conclude that the unique conjunction of stress induced by mining, the coseismic alterations of stress field and the primary stress in rock mass involving also the tectonic residual components, are the most important cause of such tremors' occurrence. Since changes of stress in rock mass during the mining process may be effectively tracked using the solutions offered by the appropriate3Dgeomechanical models (e.g. FEM), the assessment of these changes due to mining face progress is very possible also in the location where the seismic tremor has occurred and afterwards was characterized by its focal mechanism by using the appropriate geophysical methods.

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