Abstract
To overcome the problems of poor cutting effects in hard rock roadways, a cut blasting technique with large diameter charges was developed; that is, the cut holes employ 50 mm diameter blast holes and 45 mm diameter explosive sticks, while the other holes adopt 42 mm diameter blast holes and 35 mm diameter explosive sticks. First, the effect of charge diameter on damage range and cut cavity formation was analyzed. Next, simulation of wedge cut for different charge diameters was conducted to reveal the stress wave developments and compare the stress field intensities. Finally, field tests were conducted to verify the viability of this technique. The results indicate that large diameter charges can increase the damage range around cut holes to improve the fragmentation degree of the rock mass in the cut cavity and significantly enhance the cavity formation power to better expel the rock mass fragments. The stress wave evolution of wedge cut was visualized using numerical simulations, which confirmed that the use of large diameter charges in cut holes increases the stress field intensity in the cut cavity and hence increases the damage degree of the rock mass. In this study, the use of a large diameter charge for cut blasting increased the average footage by 0.30 m, and the average utilization rate of blast holes increased by 12.5%. Therefore, the cutting effects in hard rock roadways can be improved by using large diameter charges, which increase the blasting footage and the utilization rate of blast holes.
Highlights
Drilling and blasting is a traditional, efficient, and economical construction method, which is widely used in mining excavation engineering [1,2,3]
It can be seen that the radii of the crushing and cracking zones increase with charge diameter, and the damage range generated by a 50 mm diameter blast hole with a 45 mm diameter explosive stick is 1.31 times that generated by a 42 mm diameter blast hole with a 35 mm diameter explosive stick. us, further penetration of blasting cracks can be realized by large diameter charges to improve the fragmentation degree of the rock mass in the cut cavity
When the number of cut holes (m), charge length (Lc), and cut hole angle (β) remain constant, it can be calculated that the cavity formation power generated by 50 mm diameter cut holes and 45 mm diameter explosive sticks is 2.22 times that generated by 42 mm diameter cut holes and 35 mm diameter explosive sticks. erefore, for a constant cavity formation resistance, the cavity formation power of cut blasting with a large diameter charge is significantly greater than that of cut blasting with a small diameter charge, which is more conducive to expelling the rock mass fragments from the cut cavity
Summary
Bing Cheng ,1,2 Haibo Wang, Qi Zong ,1,2 Ying Xu, MengXiang Wang, Qiangqiang Zheng, and Chengjie Li1. The effect of charge diameter on damage range and cut cavity formation was analyzed. Simulation of wedge cut for different charge diameters was conducted to reveal the stress wave developments and compare the stress field intensities. E stress wave evolution of wedge cut was visualized using numerical simulations, which confirmed that the use of large diameter charges in cut holes increases the stress field intensity in the cut cavity and increases the damage degree of the rock mass. The use of a large diameter charge for cut blasting increased the average footage by 0.30 m, and the average utilization rate of blast holes increased by 12.5%. Erefore, the cutting effects in hard rock roadways can be improved by using large diameter charges, which increase the blasting footage and the utilization rate of blast holes The use of a large diameter charge for cut blasting increased the average footage by 0.30 m, and the average utilization rate of blast holes increased by 12.5%. erefore, the cutting effects in hard rock roadways can be improved by using large diameter charges, which increase the blasting footage and the utilization rate of blast holes
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