爆破震动对采空区稳定性影响的FLAC^(3D)分析

STABILITY ANALYSIS OF MINED-OUT AREAS INFLUENCED BY BLASTING VIBRATION WITH FLAC^(3D)

针对厂坝铅锌矿受到乱采乱挖破坏的情况,运用FLAC3D对爆破震动作用下采空区的稳定性进行了数值分析。根据现场实测数据,选取了2条不同的实测速度时程曲线作为爆破震动输入,分别进行了静力和动力计算。分析结果表明:(1)采空区开挖后,最大位移量为4.75mm;(2)施加爆破动载荷后,最大位移量增至5.47mm,增幅与爆破震动速度成正比;(3)围岩位移分布的变化受震动波形的影响。爆破震动作用下围岩应力场发生二次重分布,塑性区分布面积明显扩大,采空区右上方露天边坡脚亦受到影响。分析结果与实际观测结果相吻合,并给出了避免爆破震动诱发采空区失稳塌陷的几条建议。

For the reason that Changba lead-zinc mine is severely destroyed by disordered mining, the numerical analysis of mined-out areas under blasting vibration is carried out with FLAC^3D . Two different measured velocity time-dependent curves are selected as blasting vibration input according to the in-situ test data; and static calculation and dynamic calculation are carried out, respectively. The analytical results show that the maximum displacement of surrounding rock is 4.75 mm after mined-out areas are excavated, while the maximum displacement of surrounding rock increases to 5.47 mm after the blasting dynamic loading is applied, and amplitude of increasing displacement is proportional to the velocity of blasting vibration. The shape of vibration wave influences the variation of displacement distribution for surrounding rock. When the blasting vibration dynamic loading is applied, the second redistribution of stress field of surrounding rock occurs： and the distribution area of plastic zone is expanded obviously. The foot of the right open slope above the mined-out area is also influenced as well. The analytical results are accordant with the observed results. Several suggestions to avoid instability and subside of mined-out areas induced by blasting vibration are brought forward.