Numerical Simulation Of Seismic Dynamic Response Of Ground Surface Above The Goaf Of Coal Mine

Most of the coal mines are distributed in the areas of seismic intensity 7 in China. Large-scaled mined-out spaces formed in the strata of mine goaf because of large-scale coal mining exploitation. Goaf affects the propagation of seismic waves, so that the impact of the earthquake on the mine surface is different from the other places. The analysis on the impact of the seismic waves on the surface above the goaf is significant to the location of the mine industrial squares, civil buildings, the stability of the existing buildings and the environment around the mine.This paper discusses the seismic response of the surface above the goaf by theoretical analysis, data collection and numerical simulation. Based on the governing equations of the elastic waves and relative displacement method in Fourier transform method category, the reflection, transmission and scattering properties of seismic waves and analyzed. The data of the damage of the mine surface in Tangshan earthquake is sorted out and analyzed the damage by FLAC3D finally.The results show that the presence of goaf will not cause excessively strong earthquake damage to the near surface; instead the damage to the surface above the goaf is slighter, especially to the surface above the edge of the goaf, the reduce rate is about 10%. When the goaf is discontinuous, the surface damage where is about 4-5 times the size of half-width of the goaf distance away from the goaf is more severe than the surface damage in unexploited places,the amplification rate is about 8%. The surface damage where is about 8 times the size of half-width of the goaf distance away from the goaf is not affected by the goaf. When the goaf is approximate continuous, the surface damage above the goaf is slightly less severe than the surface damage in unexploited places. The surface damage is not affected by the goaf around the goaf.