基于FLAC^(3D)软件的凝灰岩矿溜井爆破降段动应力数值模拟及稳定性分析

Numerical simulation and stability analysis of dynamic stress in the descending section of tuff mine chute blasting based on FLAC^(3D) software

溜井放矿已逐渐成为砂石骨料矿山的重要出矿手段,因此对溜井的稳定性进行分析探讨有利于矿山生产工作的可持续发展。面对溜井内部结构复杂、探测难度大等问题,为更好地模拟研究溜井降段爆破方法,本文基于某凝灰岩砂石骨料矿山,采用FLAC^(3D)软件建立溜井有限差分网格模型,以溜井爆破降段过程中的动应力变化和损伤破坏位移为评判依据,对该矿溜井的降段爆破进行研究,得到了溜井低采面持续爆破降段动应力扰动下的围岩变化规律。研究表明:凝灰岩矿溜井井筒底部大部分区域存在明显应力集中;低采面长期爆破降段对溜井内部围岩造成损伤,溜井整体稳定性减小,垮塌风险显著增加;动载源距避爆点50~60 m外,采场构筑物或者岩体的震动明显减弱;随着开采水平不断下降,溜井发生冲击破坏或疲劳损伤的主要原因是动载产生的拉应力,当降段至180 m围岩时,最大位移量可达约17.83 mm。结果表明,本文建立的凝灰岩露天矿溜井模型能很好地反映溜井爆破降段的模拟效果。

Ore drawing by chute has gradually become an important ore drawing means in sandstone aggregate mines.Therefore,the analysis and discussion on the stability of chute is conducive to the sustainable development of mine production.Facing the problems of complex internal structure and difficult detection of the chute,in order to better simulate and study the blasting method of the descending section of the chute,based on a tuff sandstone aggregate mine,the finite difference grid model of the chute is established by using FLAC^(3D) software,which is based on the dynamic stress change and damage displacement during the descending section of the chute.The descending blasting of a tuff mine chute is studied,and the variation law of surrounding rock under the disturbance of dynamic stress in the descending section of continuous blasting in the low mining face of the chute is obtained.The results show that there is obvious stress concentration in most areas at the bottom of the chute shaft in tuff mine.The long-term blasting descending section of low mining face causes damage to the surrounding rock in the chute,reduces the overall stability of the chute and significantly increases the collapse risk.The vibration of stope structures or rock mass is obviously weakened 50-60 m away from the explosion avoidance point.With the continuous decline of mining level,the main cause of impact failure or fatigue damage of chute is the tensile stress caused by dynamic load.When the descending section reaches 180 m surrounding rock,the maximum displacement can reach about 17.83 mm.The results show that the chute model of tuff open-pit mine established in this paper can well reflect the simulation effect of chute blasting.