Short-delay blasting with single free surface: Results of experimental tests

Qiu, Xianyang; Shi, Xiuzhi; Gou, Yonggang; Zhou, Jian; Hui, Chen; Huo, Xiaofeng

doi:10.1016/j.tust.2018.01.014

Cited by 67 publications

(32 citation statements)

References 25 publications

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“…Drilling and blasting methods have been extensively applied to rock excavation in mining and civil engineering due to its low cost, high efficiency, and easy operation. [1][2][3][4][5]. However, some inevitable negative effects are often encountered under the blasting loads, such as blast-induced damage and vibration [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Presplit and Smooth Blasting Methods for Excavation of Rock Wells

Zhou

Cheng

Cai

et al. 2019

Shock and Vibration

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To understand differences of smooth and presplit blasting for the excavation of rock wells, two field experiments using these two techniques are implemented at the same test site, respectively. The ground vibrations induced by them have been monitored with the different distances through the corresponding devices. The vibration results illustrate that at the same monitoring distance and direction, peak particle velocities and dominant frequencies of vibration signals based on presplit blasting are both apparently lower than that based on smooth blasting. Meanwhile, with the increase of distance, the principle and mean frequencies based on smooth blasting always decrease, but these two frequencies based on presplit blasting might firstly decrease and then rise. In addition, frequency bands of energy distributions based on smooth blasting are more dispersive than that based on the presplit blasting at the same distance and direction. Lastly, the excavation qualities of rock wells with two techniques are also measured. The excavation results demonstrate that the contour quality and flatness of well bottom based on smooth blasting are better than that based on presplit blasting. Nevertheless, well depth based on presplit blasting is larger than that based on smooth blasting.

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Section: Introductionmentioning

confidence: 99%

Comparison of Presplit and Smooth Blasting Methods for Excavation of Rock Wells

Zhou

Cheng

Cai

et al. 2019

Shock and Vibration

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“…Therefore, it can be conclude that the stress wave superposition of adjacent blast holes is not an indispensable factor in the process of the formation of a common blasting crater. Based on the formation mechanism of a common blasting crater, two steps are considered to be vital: the formation of through-wall cracks between adjacent blast holes and the pushing effect of detonation gas induced by adjacent blast holes on cracked rocks in the direction of a free surface [ 26 ]. For a blast hole with fully coupled stemming in good condition, the action time for detonation gas is normally more than 10 ms [ 42 , 43 ].…”

Section: Discussionmentioning

confidence: 99%

“…In order to artificially create new free surfaces for subsequent blasts, there can be a set of blast-holes close in space and initiating at the same nominal delay time (a typical cutting blasting scheme in underground mines is shown in Fig 1 ), which results in large charge weight per delay [ 25 ]. The short delay blasting with single free surface was proposed by Qiu et al [ 26 ] to reduce the harmful vibration in underground cutting blasting. The objective of this study is to investigate the effect of stress wave interaction between blast holes with a single free surface.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of stress wave interaction in short-delay blasting with a single free surface

et al. 2018

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It is generally believed that stress wave superposition does occur and plays an important role in cutting blasting with a single free surface, in which explosive columns of several blast holes with short spacing are simultaneously initiated. However, considering the large scatter of pyrotechnic delay detonators that are used in most underground metal mines in China, the existence of stress wave superposition and the influence of this effect on rock fragmentation are questionable. In the present study, the stress wave interaction in short-delay blasting with a single free surface was studied through the use of the LS-DYNA code. Stress waves induced by two blast holes blasting with different delays were compared with the single blast hole case, and the effects of delay time, detonating location and spacing on stress wave superposition were investigated. The numerical results showed that for blast holes with a 1 m spacing, stress wave interaction only occurs when the delay time is 0 ms and does not occur for blasting with delays of more than 1 ms. An increase in the duration of a stress wave via optimizing the detonation location does not improve the stress wave interaction. For a 1 ms delay, stress wave superposition only occurs when the spacing is more than 4 m, which is a rare case in practice. The results indicated that the occurrence of stress wave superposition for blasting with a single free surface is strictly limited to conditions that would be difficult to achieve under the existing delay accuracy of detonators. Therefore, it is unrealistic to improve fragmentation via the stress wave interaction in field blasting. Furthermore, the numerical results of the stress wave interaction also show that there would be a great potential to reduce the hazardous vibrations induced by short-delay blasting by using electronic detonators with better control of delays in an order of several milliseconds.

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“…ere are numerous research studies about blasting issues under an initial stress field [6][7][8][9]. Kutter and Fairhurst [10] explored the effects of explosion stress waves and explosive gas on crack propagation to find that blast-induced cracks extend toward the direction of the maximum principal stress in the static stress field.…”

Section: Introductionmentioning

confidence: 99%

In Situ Stress Effects on Smooth Blasting: Model Test and Analysis

Yang

Fang

Yang

et al. 2020

Shock and Vibration

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Most of the roadway excavation is completed by the drilling and blasting method. With the increase of buried depth, the existence of ground stress will generate a significant impact on the rock blasting, especially on the smooth blasting. In this study, self-made homogeneous similar materials and digital image correlation methods were used to determine influence of ground stress on the smooth blasting under uniform explosive charge parameters and various in situ stress conditions. The results show that the crack outline after blasting changes from zigzag to straight in shape, and multifractal calculation results of the rupture section between blastholes show that the fracture surface becomes flatter as ground stress increases, which is conducive to roadway formation. The strain and equivalent strain rate obviously decrease as the distance between the blasthole and measuring points increases. The same trend occurs as the confining pressure goes up. Meanwhile, a postexplosion acoustic wave test indicates that confining pressure inhibits damage of the retained rock, which is consistent with strain and equivalent strain rate results. Finally, we discussed the crack propagation mechanism of rock in smooth blasting.

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Short-delay blasting with single free surface: Results of experimental tests

Cited by 67 publications

References 25 publications

Comparison of Presplit and Smooth Blasting Methods for Excavation of Rock Wells

Comparison of Presplit and Smooth Blasting Methods for Excavation of Rock Wells

Numerical simulation of stress wave interaction in short-delay blasting with a single free surface

In Situ Stress Effects on Smooth Blasting: Model Test and Analysis

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