Optimization and application of blasting networks based on rock mass classification zoning

To address the issues of blasting energy loss, high boulder rate, and high fine powder rate caused by the heterogeneous characteristics of rock mass in local areas of a plateau mine, blasting area division and network optimization are conducted based on basic rock mass mechanical parameters. Taking the NW2 mining area of the mine as an example, it is divided into three blasting zones, namely: Hard Rock Zone （Zone I）, Medium-Hard Rock Zone （Zone II）, and Soft Rock Zone （Zone III）. The rationality of this division is verified through theoretical analysis. Based on the characteristics of each zone, a differentiated “zigzag” initiation network is designed: for Zone I, a short delay is adopted to enhance the stress wave superposition effect; for Zone II, the inter-row delay is eliminated, and an inter-hole delay of 42 ms is used to achieve blasting crater expansion and backbreak control; for Zone III, a long delay is applied to reduce the strain rate and protect the surrounding rock mass. Field practice has shown that the optimized scheme makes the blasting fragment size distribution approach a normal distribution, and the boulder rate and fine powder rate are significantly reduced. This provides theoretical and technical support for the refined blasting in other areas of the mine.