The dynamic varied elastic modulus and damping coefficient of underground goaf are most important factors which describes the goaf absorption ability on seismic wave energy. This numerical simulation study have focused on the effect of goaf area on earthquake-wave propagation and seismic response on the ground surface in a coal mine area. The laboratory measurements were carried out by 135 porous samples cases consisting rocks and coal particles 0.12–0.25 mm in size to estimate the dynamic elastic modulus and damping coefficient of the fragmented rock masses. In this simulation, a new model on damping coefficient of longitudinal and transverse waves has been presented in considering rock size (D), effective stress (σe), porosity (φ) and compaction time (t). The empirical correlation between the damping coefficient and effective stress (depth) as well as the compaction time of the goaf area has been derived and used for each goaf and strata grid blocks in the simulation. The results showed that the peak ground acceleration (PGA) above the goaf area exhibits 9–20% reduction compared to that of unexcavated condition (original coal seam), and around 10–35% seismic energy is trapped in the goaf area as goaf varied from 100 to 700 m. In the meantime, the peak ground displacement (PGD) is amplified up to seven times for the goaf depth ranging from 100 to 700 m compared to that of the unexcavated condition. Both PGA and PGD above goaf area are smaller than those above the undisturbed coal seam.

中文翻译：

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地下长壁采空区上地表地震响应模拟研究

地下采空区的动态变弹性模量和阻尼系数是描述采空区对地震波能量吸收能力的最重要因素。本次数值模拟研究重点研究了采空区对某煤矿区地表地震波传播和地震响应的影响。实验室测量是通过 135 个多孔样品箱进行的，这些样品箱由尺寸为 0.12-0.25 毫米的岩石和煤颗粒组成，以估计破碎岩体的动态弹性模量和阻尼系数。在该模拟中，在考虑岩石尺寸 (D)、有效应力 (σe)、孔隙度 (φ) 和压实时间 (t) 的情况下，提出了纵波和横波阻尼系数的新模型。阻尼系数与有效应力（深度）以及采空区压实时间之间的经验相关性已经导出并用于模拟中的每个采空区和地层网格块。结果表明，与未开挖条件（原始煤层）相比，采空区上方的峰值地面加速度（PGA）降低了 9-20%，并且随着采空区的变化，约 10-35% 的地震能量被困在采空区区域从 100 到 700 m。同时，与未开挖条件相比，采空区深度范围为 100 至 700 m 的峰值地面位移 (PGD) 放大了 7 倍。采空区上方的 PGA 和 PGD 均小于原状煤层上方的 PGA 和 PGD。