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<p>Drill-and-blast tunneling in soft-hard heterogeneous rock mass leads to pronounced overbreak and underbreak issues, while concurrently impeding excavation progress in tunnel construction. These challenges primarily arise from the inadequacy of blasting parameter designs, which fail to account for the mechanical and structural heterogeneity of the rock mass. Based on tunnel excavation experiments conducted under such geological conditions, the damage characteristics of the surrounding rock were systematically investigated, considering the combined effects of soft rock, hard rock, and joint planes under blasting loads. In soft rock, the excavation depth is typically greater, whereas in hard rock, it is substantially smaller, resulting in uneven tunnel faces characterized by pronounced undulations. The presence of joint planes further exacerbates overbreak in soft rock, with the maximum overbreak exceeding the permissible limit by 164%. Numerical simulations provided insights into the dynamic failure mechanisms of the soft–hard heterogeneous rock mass under blasting loads. In hard rock, the interaction between blast-induced cracks and joint planes facilitates the formation of potential unstable fracture blocks. In contrast, in soft rock, the extensive development of fracture zones, combined with the oblique intersection of blast-induced cracks and joint planes, tends to produce M-shaped failure surfaces. To address these difficulties, a partitioned tunnel face structure was proposed, along with an asymmetric and differential blasting design. This enhanced approach refined key blasting parameters, including blasthole length, spacing, inclination, and explosive charge quantity (EQ). In addition, the use of water bags, stemming materials, and detonating cords enhanced the perimeter hole charging structure. The application of the improved blasting scheme significantly reduced overbreak, with the average linear overbreak reduced to just 56.8% of the allowable limit. The tunnel face achieved a smooth and regular profile, while ensuring equivalent excavation progress. Surrounding rock deformation and ground subsidence were effectively controlled, enabling safe and continuous tunnel excavation.</p>

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Experimental and Numerical Study on Controlled Blasting Excavation of Metro Station in Soft–Hard Heterogeneous Rock Mass

  • 期刊论文

  • 发表日期：

    2025年9月30日

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  • Wanzhi Zhang,
  • Jie Mei,
  • Bangshu Xu,
  • Xiaobo Li,
  • Shuailong Jia,
  • Shikui Jia

摘要

Drill-and-blast tunneling in soft-hard heterogeneous rock mass leads to pronounced overbreak and underbreak issues, while concurrently impeding excavation progress in tunnel construction. These challenges primarily arise from the inadequacy of blasting parameter designs, which fail to account for the mechanical and structural heterogeneity of the rock mass. Based on tunnel excavation experiments conducted under such geological conditions, the damage characteristics of the surrounding rock were systematically investigated, considering the combined effects of soft rock, hard rock, and joint planes under blasting loads. In soft rock, the excavation depth is typically greater, whereas in hard rock, it is substantially smaller, resulting in uneven tunnel faces characterized by pronounced undulations. The presence of joint planes further exacerbates overbreak in soft rock, with the maximum overbreak exceeding the permissible limit by 164%. Numerical simulations provided insights into the dynamic failure mechanisms of the soft–hard heterogeneous rock mass under blasting loads. In hard rock, the interaction between blast-induced cracks and joint planes facilitates the formation of potential unstable fracture blocks. In contrast, in soft rock, the extensive development of fracture zones, combined with the oblique intersection of blast-induced cracks and joint planes, tends to produce M-shaped failure surfaces. To address these difficulties, a partitioned tunnel face structure was proposed, along with an asymmetric and differential blasting design. This enhanced approach refined key blasting parameters, including blasthole length, spacing, inclination, and explosive charge quantity (EQ). In addition, the use of water bags, stemming materials, and detonating cords enhanced the perimeter hole charging structure. The application of the improved blasting scheme significantly reduced overbreak, with the average linear overbreak reduced to just 56.8% of the allowable limit. The tunnel face achieved a smooth and regular profile, while ensuring equivalent excavation progress. Surrounding rock deformation and ground subsidence were effectively controlled, enabling safe and continuous tunnel excavation.