Theoretical study of the influence of empty-hole on both the blasting parameters and the blasting effect of straight-hole cutting

ZHANG Zhaoran; WANG Yan; LIU Guoqing

doi:10.11883/bzycj-2021-0519

Volume 43 Issue 1

Jan. 2023

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ZHANG Zhaoran, WANG Yan, LIU Guoqing. Theoretical study of the influence of empty-hole on both the blasting parameters and the blasting effect of straight-hole cutting[J]. Explosion And Shock Waves, 2023, 43(1): 015201. doi: 10.11883/bzycj-2021-0519

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ZHANG Zhaoran, WANG Yan, LIU Guoqing. Theoretical study of the influence of empty-hole on both the blasting parameters and the blasting effect of straight-hole cutting[J]. Explosion And Shock Waves, 2023, 43(1): 015201. doi: 10.11883/bzycj-2021-0519

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Theoretical study of the influence of empty-hole on both the blasting parameters and the blasting effect of straight-hole cutting

doi: 10.11883/bzycj-2021-0519

1.
School of Civil Engineering, North China University of Technology, Beijing 100144, China
2.
Beijing Residential Group Co., Ltd, Beijing 100101, China
3.
China North Blasting Technology Co., Ltd., Beijing 100089, China

Received Date: 2021-12-20
Rev Recd Date: 2022-05-05

Available Online: 2022-09-08

Publish Date: 2023-01-05

Abstract

Abstract

The paper is aimed to determine the distance between blast holes (a) and the distance between boreholes and the empty holes (L) in the straight-hole cutting with empty holes. Firstly, by considering the crack mainly being fractured during the quasi-static expansion of explosion gas and the effect of empty hole, the calculation formula of the crack length is derived; and then, the calculation formulas of the distance between boreholes and the distance between blast holes and the empty hole are determined. Moreover, the formula of the length of the crack zone around the empty hole in the straight-hole cutting with large empty holes is obtained, and the criterion of the radial crack at the blasting side of the empty hole is established based on the effect of stress concentration around empty hole. Secondly, by considering two different design ideas, the blasting parameters and cut blasting effect are compared and analyzed for the blasting in both limestone (hard rock) and mudstone (soft rock),while the reliability of the theoretical analysis is verified by engineering practice. The results show that the rock breaking mechanism of straight-hole cut blasting with empty hole is different under the two design ideas. Namely, if a is taken as the main factor, then the coalescence of cracks between adjacent boreholes is the key factor to the formation of the cavity, whilst if L is taken as the main factor, the bore holes and empty holes are preferentially penetrated to form the cavity based on the empty hole effect. In addition, the contributions of stress wave (dynamic action) and detonation gas (static action) to the crack length in both hard rock and soft rock are about 4∶1 and 9∶1, respectively. Considering the empty hole effect, the flake fracture zone in soft rock is larger than that in hard rock, to which more attention should be paid in the design of blasting parameters. Whereas, the critical length of radial crack initiated from the empty hole is less than the sum of the blasting crack length from cutting hole and the radius of empty hole, so that the radial cracks initiated from the empty hole will not be generated, which can be ignored in the blasting parameter design. The results indicate that the two different design ideas have great influence on cutting blasting parameters and blasting effect, and the calculation model of blasting crack length based on the driven of detonation gas can provide a good reference for the design of blasting parameters.
- rock roadway excavation,
- cut blasting,
- empty-hole with large diameter,
- blasting parameters,
- fracture shape

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References(20)

References

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