既有临空面对采空区上覆岩体爆破振速场的影响研究

采空区边界条件影响其上覆岩体爆破地震效应。基于弹性波动理论,借助动力有限元算法,研究了采空区临空面、地表自由面及两种边界耦合作用下爆破地震波的传播机制与上覆岩体振速场的空间分布规律,以此为理论依据提出了上覆岩体分区准则。结果表明:采空区临空面改变爆破地震波传播路径,拐点对爆破地震效应具有显著衰减作用,可根据波传播途径拐点数对围岩分区;爆破地震波传播至地表自由面反射,对采空区上覆岩体爆破地震效应具有放大作用。提出将爆破振动作用下采空区上覆岩体的影响范围划分为两区:I区-波直传爆破振动放大区,Ⅱ区-波传播单拐点爆破振动弱衰减区,耦合作用下采空区临空面衰减作用大于地表自由面放大作用。上覆岩体爆破影响分区准则对地下工程爆破设计施工有一定指导意义。

Influence of Existing Free Face on Blasting Vibration Velocity Field of Overlying Goaf Stratum

Blasting seismic effect in overlying stratum is influenced by the boundary condition of underground goaf.By theoretical analysis and numerical simulation,the propagation mechanism of blasting seismic wave and spatial distribution of vibration velocity field were investigated under different boundary conditions.A criterion for influential partitions of blasting vibration was proposed according to the basic theories of propagation and attenuation of blasting vibration field.Results proved that the propagation path of blasting seismic waves was influenced by the free surface of underground goaf,and the blasting seismic effect was significant declined by the wave-path inflection point.The number of inflection points was a key factor for partitions of surrounding rock mass.The existence of ground surface had free surface effect on the overlying goaf stratum,which resulted in a magnification of blasting seismic effect on overlying rock mass.Considering the interaction between free surface of goaf and ground surface on wave propagation,the overlying stratum can be divided into two zones:Zone I is a magnified blasting vibration field and ZoneⅡis a weak-attenuated blasting vibration field.The proposed criterion has a guiding significance for blasting hazard control and blasting design optimization.