A programme of study was taken up to investigate the influence of surface blasting on underground coal mine openings and to suggest optimal blast design to avert any damage there to. A number of opencast blasts at all the operating faces i.e. shovel benches, dragline bench and coal benches were conducted in close vicinity to underground openings. The strata monitoring equipments were installed in the underground mine to monitor the strata behaviour. Altogether 78 blasts were performed with varying blast designs and charging patterns and 257 ground vibration data were generated. The analyses of vibration data indicate that roof of the underground openings vibrated with higher amplitude compared to pillar of the underground mine. Choked face blasting generated much higher ground vibrations than the free face blasting. It was observed that spalling of coal chips from roof started at peak particle velocity of 121 mm/s. A coal block of size 0.25 m~3 got detached from roof at the peak particle velocity of 243 mm/s. Strata monitoring study was continued for 11 months but it did not indicate any abnormal change in strata behaviour. Based on the analysis of data blast designs were recommended for all the operating benches to get optimum results ensuring the safety of underground workings.
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机译：进行了一项研究计划，以研究露天爆破对地下煤矿井口的影响，并提出最佳的爆破设计，以防止对地下煤矿的破坏。在所有工作面附近的地下开口处进行了许多露天爆炸，即铲子工作台，拉斗铲工作台和煤工作台。地层监测设备安装在地下矿井中以监测地层行为。使用不同的爆破设计和装药模式共进行了78次爆炸，生成了257个地面振动数据。振动数据分析表明，与地下矿井的支柱相比，地下洞室的屋顶以更高的振幅振动。 face面爆破比自由面爆破产生更大的地面振动。观察到，从顶板开始以121 mm / s的峰值粒子速度散布煤屑。峰值速度为243 mm / s时，0.25 m〜3大小的煤块从顶板上脱落。地层监测研究持续了11个月，但并未显示出地层行为的任何异常变化。基于对数据的分析，建议对所有操作台进行爆破设计，以获得最佳结果，从而确保地下作业的安全。
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