Abstract
To investigate the advantages of shaped charge blasting compared to traditional smooth blasting in multi-jointed tunnels, four double-hole smooth blasting and shaped charge blasting models were established to study the influence law of the angle between joints and the line connecting blastholes on overbreak/underbreak in multi-jointed tunnel blasting, and to explore hazardous locations during tunnel cross-section blasting excavation. The research results demonstrate that smooth blasting exhibits significant damage in multi-jointed shale tunnels, leading to a substantial increase in overbreak/underbreak. Particularly when the direction of the line connecting blastholes forms a 45° angle with the joints, smooth blasting produces the maximum overbreak/underbreak, reaching 1436 cm². Therefore, such angular conditions should receive special attention in blasting scheme design. Shaped charge blasting causes less damage to surrounding rock in multi-jointed shale tunnels and can effectively reduce overbreak/underbreak during blasting, with the tunnel overbreak/underbreak decreasing by an average of 1090 cm². Particularly in the 45° angle model, it reduces overbreak/underbreak by 1161.4 cm² compared to smooth blasting, demonstrating significant optimization effects. In summary, the application effect of shaped charge blasting in multi-jointed shale tunnels is significantly superior to traditional smooth blasting. It not only effectively reduces surrounding rock damage but also significantly decreases overbreak/underbreak, thereby improving the safety and efficiency of tunnel construction. Therefore, it is recommended to prioritize the adoption of shaped charge blasting technology in practical engineering applications.
Full Text
Preamble
Comparative Study on Overbreak and Underbreak Effects of Shaped Charge Blasting and Smooth Blasting in Multi-Jointed Tunnels
YANG Hongyin
China Railway 16th Bureau Group Fourth Engineering Co., Ltd., Beijing 101400, China
Abstract
To investigate the advantages of shaped charge blasting over conventional smooth blasting in multi-jointed tunnels, four double-hole models were established for both blasting methods. These models examined how the angle between rock joints and the line connecting blast holes affects overbreak and underbreak in multi-jointed tunnel blasting, and identified hazardous locations during tunnel cross-section excavation.
The results demonstrate that smooth blasting caused significant damage in multi-jointed shale tunnels, leading to substantially increased overbreak and underbreak. This effect was most pronounced when the line connecting blast holes formed a 45° angle with the joints, where smooth blasting produced the maximum overbreak/underbreak area of 1436 cm². Therefore, special attention should be paid to this angle condition in blasting design.
Shaped charge blasting, in contrast, caused less damage to surrounding rock in multi-jointed shale tunnels and effectively reduced overbreak and underbreak. On average, tunnel overbreak/underbreak was reduced by 1090 cm², with a reduction of 1161.4 cm² in the 45° angle model compared to smooth blasting, demonstrating significant optimization.
In summary, shaped charge blasting demonstrates superior performance over conventional smooth blasting in multi-jointed shale tunnels. It not only effectively reduces surrounding rock damage but also significantly decreases overbreak and underbreak, thereby improving tunnel construction safety and efficiency. Therefore, shaped charge blasting technology is recommended as the preferred method in practical engineering applications.
Keywords: rock joints; tunnel; shaped charge blasting; smooth blasting; overbreak and underbreak