摘要:
为探究槽腔深度对掘进断面后续破岩特性的影响,将具有不同深度槽腔的掘进断面简化为含不同深度空腔的砂岩试件,采用分离式霍普金森压杆(SHPB)试验系统进行动态压缩试验,分析试件动态力学性能、能量耗散特征及破碎形态的变化规律,进而优化现场掏槽爆破参数。结果显示:对于空腔直径为10 mm和20 mm的砂岩试件,随空腔深度增加,动态峰值应力分别下降17.69 %和39.05 %、动态峰值应变各自增大7.58 %和18.56 %,耗散能分别提高22.87 %和45.92 %,耗散能密度各自提升26.92 %和73.08 %,且试件破碎块度逐渐减小,表明增加槽腔深度可降低后续岩体的抗破坏能力、增大其变形能力和能量利用率、改善其破碎效果;当空腔直径为20 mm时,试件的动态力学性能和能量耗散特征随空腔深度的变化速率更快,破碎块度更小,表明增大槽腔直径也有利于破岩;现场采用孔内-孔外复合延期掏槽爆破技术,可提高槽腔深度与直径以提供充足自由面,进而促使全断面炮孔利用率达96.1%,且保证岩石破碎块度均匀合理。
Abstract:
To investigate the influences of cutting cavity depth on subsequent rock breaking properties in driving sections, driving sections with different depths of cutting cavities were simplified as sandstone specimens with different depths of cavities. A series of dynamic compression tests were conducted using the split Hopkinson pressure bar (SHPB) testing system. Then, the dynamic mechanical properties, energy dissipation characteristics, and fracture patterns of the specimens were analyzed as the cavity depth varied, and the field cutting blasting parameters were optimized accordingly. The results demonstrate that for sandstone specimens with cavity diameters of 10 mm and 20 mm, as the cavity depth increases, the dynamic peak stress decreases by 17.69% and 39.05%, the dynamic peak strain increases by 7.58% and 18.56%, the dissipation energy increases by 22.87% and 45.92%, the dissipation energy density increases by 26.92% and 73.08%, respectively. And the fragmentation size of the specimens gradually decreases. These findings indicate that increasing cutting cavity depth could reduce the rock mass's resistance to failure, enhance its deformation capacity and energy utilization efficiency, and improve its fragmentation effects. When the cavity diameter is 20 mm, the dynamic mechanical properties and energy dissipation characteristics of the specimens change at a faster rate with the increase of cavity depth, and the fragmentation size is smaller. This indicates that increasing the cutting cavity diameter is also beneficial for rock breaking. In the field, the cutting blasting technique with hole-inner and hole-outer composite delays is adopted, which can increase the cavity depth and diameter to provide sufficient free surfaces for subsequent borehole blasting, thereby increasing the hole utilization rate of the full section blasting to 96.1%, and ensuring uniform and reasonable rock fragmentation degree.