Initial results of the seismic response modeling for the surface objects affected by mining seismicity are presented in this paper. The numerical system Plaxis (Holland) based on the FEM was used for this purpose. The excavated coal deposits in the Karvina mine district are situated close to populated areas and this excavation can be manifested into the macroseismic effects on the surface. These effects can cause the troublesome physiological feeling of inhabitants and, optionally, the failures on the buildings.
First-rate simulation of time-dependent interaction between acting element and response of loaded element are important part on geotechnical balances. The more superior is this simulation, the more obtained results agreed with reality. One of software in geotechnical practice, which satisfies exacting standards of first-rate simulation, is the Dutch product called Plaxis. This numerical system is based on Finite Element Method. Range of modeled geotechnical problems is very extensive and it is possible to appear these applications in technical papers very often. In this contribution, we are presenting first results that were obtained within simulation of seismic response of building loaded by mining induced seismicity. Numerical system Plaxis was chosen because it is possible to solve with this software both dynamic vibrations produces by natural earthquakes and human activity (induced and technical events).
Presented calculations are based on real geological and seismological conditions. Region of Karvina part of the Upper Silesian Basin, North Moravia, in which intensive mining induced seismic events are documented for a long time (Holub 1995, Kalab & Knejzlik 2002), is our test area. Underground exploitation of black coal in this region is implicating changes in configuration of stress-strain conditions in rock massif. Subsequently, overrun of limiting state of elastic parameters can evoked brittle fractures and radiation of seismic energy (mining induced seismic event). These events (called also seismic events, rock bursts, anomalous geomechanical events...) have similar character as weak natural earthquakes and they are closely connected in space and time with current mining activities. The origin of seismic events t.hat are induced by mining activity, however, may be seen also after longer period when the underground works were closed, because the stress-strain condition in rock massif must reach to totally stable stage. Responses of the rock massif on mining activities are very different according to particular locality in dependencies on rock composition, physical and technological parameters.
Mining induced seismicity in Czech Republic is observed in Karvina region, formerly also in Kladno and Pribram region; the most intensive rock burst occurred in CSA Mine in Karvina region in 1983 (local magnitude 3.8). At present, seismic network records in Karvina region up to 50 thousand seismic events per year, approximately 100–500 events of these ones have seismic energy greater than 9E3 J (local magnitude about I). Current results of seismological monitoring of manifestations of mining induced seismicity at surface objects in Karvina region demonstrate indispensable vibration effect on surface. Local geological pattern has significant influence on maximum measured amplitudes (Kalab & Knejzlik 2001, Kalab 2004).