Characteristics of the impact pressure of the hole wall by interval charge at the hole bottom

LOU Xiaoming; GUAN Xuhui; ZENG Lingfeng; GUO Wenkang; YUE Bin; LU Wei

doi:10.11883/bzycj-2022-0109

Volume 43 Issue 6

Jun. 2023

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LOU Xiaoming, GUAN Xuhui, ZENG Lingfeng, GUO Wenkang, YUE Bin, LU Wei. Characteristics of the impact pressure of the hole wall by interval charge at the hole bottom[J]. Explosion And Shock Waves, 2023, 43(6): 065201. doi: 10.11883/bzycj-2022-0109

Citation:

LOU Xiaoming, GUAN Xuhui, ZENG Lingfeng, GUO Wenkang, YUE Bin, LU Wei. Characteristics of the impact pressure of the hole wall by interval charge at the hole bottom[J]. Explosion And Shock Waves, 2023, 43(6): 065201. doi: 10.11883/bzycj-2022-0109

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Characteristics of the impact pressure of the hole wall by interval charge at the hole bottom

doi: 10.11883/bzycj-2022-0109

LOU Xiaoming^{1, 2
,},
GUAN Xuhui^{1, 2
,
,},
ZENG Lingfeng³,
GUO Wenkang³,
YUE Bin³,
LU Wei³

1.
Zijin School of Geology and Mining, Fuzhou University, Fuzhou 350116, Fujian, China
2.
Institute of Explosion Technology, Fuzhou University, Fuzhou 350116, Fujian, China
3.
Zijin Mining Construction Co., Ltd., Xiamen 361026, Fujian, China

Received Date: 2022-03-22
Rev Recd Date: 2022-04-22

Available Online: 2022-05-05

Publish Date: 2023-06-05

Abstract

Abstract

On the premise of a good crushing effect, reducing the rock mass vibration above the bottom of the upward fan-shaped deep hole by reducing the peak pressure of the shock wave at the bottom of the hole is an effective measure to protect the superstructure. To determine the reasonable length of the air column at the bottom of the hole, the influence of air column length on the impact pressure of the hole wall without consideration of air column coupling is studied by combining the theoretical analysis with the field model blast experiment. Based on the theories of one-dimensional unsteady hydrodynamics and theoretical detonation physics, the action process and propagation law of the shock wave in the blast hole in different stages after the explosion of the bottom air interval cylindrical charge column are discussed. Considering the reflection and transmission of shock waves at different media interfaces, the parameters of the shock wave propagating in different directions, the initial shock pressure, and the action time of the hole wall pressure in each stage are analyzed. Thus, the calculation formula and variation curves of the pressure on the hole wall in each stage are obtained. Six groups of twelve cylindrical thick wall concrete models of different sizes were designed and made, and the bottom air interval blasting model experiments were carried out to verify the above results. The air column lengths were 200, 400, 600, 800, 1 000 and 1 200 mm. During the blasting process, an ultra-high-speed multi-channel dynamic strain testing system was used to monitor the hole wall impact pressure. The monitoring data are then analyzed, and the theoretical results are verified. Finally, the variation curves of the peak pressures with the axial uncoupling factor and the variation curves of hole wall impact pressure with time and measurement point under different uncoupling factors are obtained. Based on the dynamic compressive strength of rock, reasonable length ranges of bottom axial air interval suitable for soft, medium, and hard rocks are determined. A field industrial blasting experiment was carried out with the air interval at the hole bottom to verify the rationality of the conclusion. The roof forming and the blasting pile size after the blast are observed and analyzed by photography. The research results show that the existence of air interval significantly increases the action time of the impact pressure. The peak value of the impact pressure decreases obviously. When the uncoupling factor is 1.5 and the length of the air column is 200 mm, the attenuation ratio of the peak pressure at the hole bottom is 73.4%; when the uncoupling factor is 4 and the length of the air column is 1.2 m, the attenuation ratio of the peak pressure at the hole bottom reaches 96.7%. When the air interval is greater than 60 cm, an area with low pressure appears at the bottom of the blast hole. A reasonable bottom air interval length can not only ensure good blasting fragmentation but also reduce blasting vibration by reducing the peak pressure at the hole bottom, thus protecting the stope roof and other protected objects.
- bottom air gap,
- axial uncoupling charge,
- air interval charge blasting,
- impact pressure

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References(24)

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