Rock fragmentation was examined for determining how stemming length affected blast effect.The formula for calculating borehole stemming length range was deduced with the momentum theorem.The tests for rock blasting with parallel double-free-surface were simulated with the finite element software ANSYS/LS-DYNA where the multi-material ALE method was used.A four-meter deep and four-hole infinite rock mass model was established.After analyzing the peak stress of the element nearby the free surface and the stress distribution of the rock,it was shown that the optimal explosive length is 2.4 m in a borehole model test without stemming;in the borehole model with one-sided stemming or asymmetric double-sided stemming,blasting has no effect on the stress distribution law of rock mass,but the peak stress of the element near the free surface increases and the acting time is lengthened;the optimal stemming length of the model with symmetric double-sided blast hole is 1 .0~1 .2 m;the blasting effects of numerical simulation results is the best compared with engineering blast effects with different parmeters,the correctness of numerical simulation results is verified.%为研究平行双自由面岩体炮孔堵塞效应，借助动量定理推导出炮孔堵塞长度范围计算公式；利用有限元软件LS-DYNA，采用ALE多物质算法，建立4 m深的四孔无限岩体模型。通过分析自由面附近单元应力峰值和岩体应力分布规律，得到：炸药长度为2．4 m的无堵塞炮孔爆破效果最优；1．2 m炸药长度的炮孔模型中，单向堵塞和非对称堵塞爆破对岩体的应力分布规律无影响，但岩体自由面附近单元的应力峰值增大，作用时间加长；双向对称堵塞的最佳堵塞长度为1．0～1．2 m。对比不同参数下的工程爆破效果，采用数值模拟结果的工程爆效最优，证明了数值模拟结果的正确性。
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