This study establishes a multiple degrees-of-freedom structural dynamics analytical model to analyse the influence mechanism of different factors on blasting tight bottom and shape of muckpile. The structural displacement response and distribution of internal forces in the bench rock mass are analysed based on several factors including blasting parameters, explosion load, initiation condition, and geological condition. In addition, the structural failure characteristics of the bench rock mass are studied based on a rock strength criterion. The results indicate that the explosive load strength determines the internal forces of the bench rock mass. The use of blasting parameters with large borehole spacing and small row spacing can increase the internal force and deformation of the bench rock and enhance the effect of the breaking and throwing of rock mass. In addition, the strengthening of the lithology of the bottom rocks or weakening of the lithology of the middle rocks can make destroying the bottom rock mass more difficult and increase the probability of blasting tight bottom formation. Adjusting the initiation point to below the weak-lithology segment of the bench can enhance the internal force and displacement of the bottom rock mass, to improve the blasting effect and avoid blasting tight bottom formation. Combined with the bench blasting field test of the Changjiu limestone mine, it verifies the results of the theoretical analysis of the bench blasting rock mass destruction based on structural dynamics. The results can be used as the theoretical basis and technical support for improving the bench blasting effect.

本研究建立了多自由度结构动力学分析模型，分析了不同因素对爆破密底和碎石堆形状的影响机制。基于爆破参数、爆炸载荷、起爆条件和地质条件等几个因素，分析了台岩体中结构位移响应和内力分布。此外，基于岩石强度准则研究了阶岩体的结构破坏特征。结果表明，爆炸载荷强度决定了阶岩体的内力。采用大孔距、小排距的爆破参数，可以增加台岩的内力和变形，增强岩体的破碎抛掷效果。此外，底岩岩性的加强或中岩岩性的减弱，会使破坏底岩体更加困难，增加爆破致密底地层的概率。将起爆点调整到平台弱岩性段以下，可以增强底部岩体的内力和位移，提高爆破效果，避免爆破致密地层。结合昌九石灰石矿台架爆破现场试验，验证了基于结构动力学的台架爆破岩体破坏理论分析结果。研究结果可为提高台架爆破效果提供理论依据和技术支持。