During tunnel blasting at deep depths, the rock mass is frequently subjected to high in-situ stress. Except for explosive detonation, the in-situ stress itself, particularly the stress concentration due to stress redistribution, also possesses the potential to cause rock fracture. Then there is a possibility of utilizing the stress redistribution to assist rock fragmentation during blasting. However, this concept has not garnered sufficient attention and systematic research in the field of tunnel blasting. The present study numerically investigated the rock fracture resulting from blasting with assistance of stress redistribution under various in-situ stress conditions with a focus on the full-face blasting of a deep circular tunnel. Based on the numerical modeling, the blasting parameter change required to maximize the auxiliary effect of in-situ stress redistribution was discussed. The results show that blasting of the previous round of blastholes creates a temporary cavity that induces in-situ stress redistribution. The redistributed stress generates cracks in the rock mass assigned to blasting of the current round of blastholes, particularly under high and anisotropic in-situ stress as well as large cavity conditions. The presence of these pre-generated cracks, together with their enhanced reflection of explosion stress waves, contributes to an increase in the degree of rock fragmentation during blasting. By utilizing the auxiliary effect of in-situ stress redistribution, there is a significant reduction in the amount of explosive required, with a saving of up to 30% demonstrated in the used computation example. The assistance of in-situ stress redistribution on rock blasting is particularly pronounced in the rock mass aligned along the orientation of minor principal stress and with larger cavities. As a result, increasing the blasthole burden in the orientation of minor principal stress and equipping the blastholes in the outer rounds with a larger burden contribute to maximize the auxiliary contribution of in-situ stress redistribution and expand the scope of rock fragmentation during blasting.

中文翻译：

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地应力重分布辅助岩石爆破数值研究


在深部隧道爆破过程中，岩体经常受到高地应力的作用。除爆炸爆炸外，地应力本身，特别是应力重新分布引起的应力集中，也具有引起岩石破裂的潜力。然后就有可能在爆破过程中利用应力重新分布来辅助岩石破碎。然而这一概念在隧道爆破领域尚未得到足够的重视和系统的研究。本研究对各种地应力条件下的应力重新分布辅助下爆破引起的岩石破裂进行了数值研究，重点是深部圆形隧道的全断面爆破。基于数值模拟，讨论了最大化地应力重分布辅助效果所需的爆破参数变化。结果表明，前一轮炮孔的爆破产生了一个临时空腔，导致地应力重新分布。重新分布的应力会在当前一轮炮孔爆破所分配的岩体中产生裂缝，特别是在高且各向异性的地应力以及大空腔条件下。这些预先产生的裂纹的存在，加上它们对爆炸应力波的增强反射，导致爆破过程中岩石破碎程度的增加。通过利用原位应力重新分布的辅助作用，所需的炸药量显着减少，在所使用的计算示例中节省了高达 30%。 地应力重新分布对岩石爆破的帮助在沿较小主应力方向排列且具有较大空腔的岩体中尤其明显。因此，增加小主应力方向的炮孔荷载，并在外圆炮孔配备较大的荷载，有助于最大限度地发挥地应力重分布的辅助作用，扩大爆破时岩石破碎的范围。