充填体相邻采场低扰动爆破参数优化及应用

Optimization and Application of Low Disturbance Blasting Parameters in Stopes Adjacent to Backfill

针对李楼铁矿二步回采爆破安全问题,利用有限元软件ANSYS/LS-DYNA建立相应的爆破模拟方案,按照现场实际采场规格,两侧充填体长度为20 m,中间回采矿体长度为30 m,底部巷道规格为4 m×4 m,充填体与矿体高度均为25 m,厚度设置与排间距一致均为2 m;布置炮孔时,考虑在矿体靠近充填体边界处内部设置0.5 m、1.0 m、1.5 m与2.0 m厚度的保护层(即炮孔底部与充填体边界处之间的矿体),同时设置孔底起爆与孔口起爆方案。模拟不同方案下二步回采炸药起爆后,在充填体边界处相应位置选取受爆破影响最大的单元进行应力、振速与位移综合分析,从而对不同方案下充填体整体稳定性进行评价。模拟结果表明:在适当范围内增大保护层厚度能够有效降低爆破对于充填体的冲击,同时,孔口起爆方案由于炸药起爆位置相对距离充填体更远,其应力波与冲击波衰减后对充填体影响更小。采用孔口起爆方案,保护层厚度设置为1.0 m时,各监测点在爆破过程中有效应力峰值为0.03 MPa,振速峰值为9.35 cm/s,合位移峰值为0.07 mm,均处于充填体安全判定范围内,而采用孔底起爆方案时保护层厚度需增至1.5 m才能使得各监测点单元处于安全状态内,相对比之下孔口起爆方案保护层厚度更小,对于矿石回收率有着更大的增益。通过现场工业试验对于孔口起爆方式,保护层厚度为1.0 m的模拟方案进行验证:在采场周边布置测振仪,根据相关数据与萨道夫斯基公式拟合得充填体边界监测点单元振速峰值为9.37 cm/s,与模拟结果中对应监测点振速峰值相符合,且现场爆破效果较为良好,进一步验证了模拟结果的可靠性与模拟方案的合理性。

Aiming at the safety problem of second-step mining blasting in Lilou Iron Mine,the finite element software ANSYS/LS-DYNA is used to establish a corresponding blasting simulation scheme.According to the actual stope specifications,the length of the backfill body on both sides is 20 m,and the length of the middle mining body is 30m.The size of the bottom roadway is 4 m 4 m.The height of the backfill body and the ore body are both 25 m,and the thickness and row spacing are both 2 m.When arranging blast holes,it is considered to set 0.5 m、1.0 m、1.5 m and 2.0 m thick protective layer(that is,the ore body between the bottom of the blasthole and the boundary of the filling body)inside the ore body near the boundary of the backfill body,and both bottom and top initiation are used.After simulating the second-step recovery blasting under different schemes,the element most affected by blasting is selected at the corresponding position of the boundary of the backfill body for comprehensive analysis of stress,vibration velocity and displacement,so as to evaluate the overall stability of the backfill body under different schemes.The simulation results show that increasing the thickness of the protective layer in an appropriate range can effectively reduce the impact of blasting on the filling body.At the same time,under the top initiation scheme,the detonation position of the explosive is far away from the filling body,and the stress wave attenuation is more obvious.When the thickness of the protective layer is set to 1.0 m under the top initiation scheme,the effective stress peak value,the peak vibration velocity,and the peak value of the combined displacement of each monitoring point during the blasting process are 0.03 MPa,9.35 cm/s,and 0.07 mm respectively,all of which are in the safety range of the filling body.However,the thickness of the protective layer needs to be increased to 1.5 m when the bottom initiation scheme is adopted to keep each monitoring point in a safe state.In contrast,the thickness of the protective layer of the top initiation scheme is smaller,which has a better effect on the ore recovery rate.The simulation scheme of the top initiation method and the thickness of the protective layer of 1.0 m is verified through the field industrial tests by arranging a vibration meter around the stope.And the peak particle vibration velocity at the backfill boundary is fitted according to the relevant data and the Sadowsky formula.The peak velocity is 9.37 cm/s,which is consistent with the peak vibration velocity of the corresponding monitoring point in the simulation results.And the blasting effect on site is relatively positive,which further verifies the reliability of the simulation results and the rationality of the simulation scheme.