Results of Ground Motion Measurements Close to the Sources of Mining Tremors

摘要

The aim this study is to obtain ground motion characteristics for near distances, i.e., at locations affected by the rockburst-related failures. Such characteristics and the knowledge of the ground motion peak particle velocity (PPV) are of great practical importance for the comprehensive rockburst prevention. Also, it follows from the experiments that the PPV values can be utilized to estimate the state of rockburst hazard. The results of special seismic measurements conducted in several hard coal mines show that in rock mass regions at short distances from the tremor sources the ground motions are characterized by very high PPA and PPV values and by the prevalent high frequency spectral components. In the Upper Silesian Coal Basin, the results of the study of mining tremors close to the sources can be summarized as follows: 1. The PPV values are 150 mm/s (when prevalent frequency f_D does not exceed 100 Hz) and 380 mm/s (when f_D exceeds 100 Hz), 2. The PPA value (obtained after differentiation of the velocity seismogram, filtered in the frequency range of 1-100 Hz) is 42 m/s~2 (almost five times as large as the acceleration of gravity), 3. The amplification of the PPV at the boundary between the cracked coal zones around openings and hard rock (sandstone) was often fourfold. It is expected that these parameters will allow to develop more real empirical and analytical criteria of the ground failure (rockburst) occurrence.