露天矿地下采空区爆破崩落法治理效果的数值模拟研究

摘要

爆破崩落法是治理露天矿地下采空区的主要手段,数值模拟是研究爆破崩落效果的有效工具.基于连续-非连续数值模拟方法(CDEM),利用朗道点火爆炸模型实现了炸药起爆过程的描述,利用考虑应变软化效应的Mohr-Coulomb模型及最大拉应力模型实现了围岩损伤破裂过程的模拟.以弓长岭铁矿何家采场采空区为研究对象,重点探讨了炮孔间排距、起爆延时等对该采空区上覆岩层损伤破裂程度、空区填充程度及空区内大块率的影响规律.计算结果表明:炮孔间排距对爆破效果的影响较大,随着间排距的增大,塌落至空区的大块率逐渐增大,且塌落范围逐渐减小.当间排距为17 m时,仅空区顶板附近出现局部塌落,地表岩层依然处于稳定状态.起爆延时对爆破效果的影响较小,当起爆延时大于42 ms以后,塌落至空区的岩体块度分布基本一致,仅大块率有所区别.为了确保爆破崩落法的治理效果,建议炮孔的间排距不大于7 m,炮孔排间延时不小于42 ms.%Blasting caving is the main method to control the underground goafs in open pit mine,and the numeri-cal simulation is an effective tool to study the blasting effect.Based on the Continuous Discontinues Element Method (CDEM),the Landau blasting model was adopted to describe the detonating process of explosives.The Mohr-Cou-lomb model and maximal tensile stress model considering strain softening effect are used to simulate the damage and fracture process of rocks.Based on the goafs in Hejia stope in Gongchangling iron mine,the damage and fragmenta-tion degree,filling degree,and large block ratio in goaf affected by row-column spacing of bore holes and detonating delay is discussed.The numerical results show that the row-space of hole influence the blasting quality greatly.With the increment of spacing,the large block ratio in goaf increases gradually,and the collapse area decreases gradually. When the row-space of hole reaches 17m,local collapse just appears near the roof of goaf,and the surface of the rock layer is still stable.Detonating delay will not affect the blasting results so seriously.When delay time is greater than 42ms,the distribution of fragments in goaf is approximately the same,except the little difference in large block ratio.To ensure the control effect of blasting caving method,it's suggested that the row-space of hole should not be greater than 7m,and initiation delay should not be less than 42 ms.