Experimental Study on the Influence of Delay Time on Rock Fragmentation in Bench Blasting

Tang, Hongliang; Liu, Xin; Yang, Jun; Yu, Qi

doi:10.3390/app13010085

Cited by 8 publications

(5 citation statements)

References 43 publications

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“…Each end of the tube was wrapped with black tape to form a lining equal to the diameter of the borehole to make sure the explosive column was positioned at the center of the borehole. In order to provide accurate delayed initiation between boreholes, the initiation timing of the explosive columns in the boreholes was controlled by changing the length of detonating cord, referring to the detonation method used in previous studies [27,30]. According to the information from the supplier, the detonating cord had a linear density of 4.25 g/m and a detonation velocity of 6850 m/s.…”

Section: Specimen and Explosivementioning

confidence: 99%

“…Their results indicated that the best fragmentation could be obtained by detonating the second blast hole when the damage process of the first blast hole reached its final state. Tang et al [30] used double-hole bench specimens to study the influence of delay time on rock fragmentation. Their study indicated that a long delay without stress wave superposition obtained the best blasting excavation quality.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation of the Effect of Delay Time on Rock Fragmentation in Multi-Hole Bench Blasting

Tang

Yang

2023

Applied Sciences

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Rock fragmentation by blasting influences ore recovery and the cost of downstream operations. The development of electronic detonators makes it possible to improve fragmentation by controlling the initiation timing in blasting projects, and the effect of the mechanism of delay timing on rock fragmentation should be studied. Fragmentation of granite bench specimens with different initiation timing was investigated in blast experiments. Conclusions are obtained by studying the surface strain field and post-blast specimens. A total of six blasting tests were carried out on granite bench specimens with four boreholes each having a diameter of 10 mm and a length of 450 mm. Each borehole used pentaerythritol tetranitrate (PETN) as the explosive charge, which was approximately 4.84 g with a charge diameter of 5.5 mm. Delay times between adjacent boreholes in the same row were set as 0, 50, 100, 150, 200, and 250 µs. The surface strain field of the bench specimen under blast loading was analyzed using three-dimensional digital image correlation (3D-DIC) techniques based on two cameras that captured high-speed images. Additionally, the post-blast specimen was also observed and recorded. Fragments of each bench specimen were carefully collected, weighed, and sieved with a set of sieves, including very fine particles. According to the 3D-DIC analysis for bench specimens, the propagation pattern of the main strain concentration zone transformed from horizontal to vertical with the increase in inter-hole delay. The maximum blast excavation weight was obtained by the bench specimen with an inter-hole delay of 100 µs, while the bench specimen with the longest inter-hole delay (250 µs) obtained the minimum blast excavation weight. By combining the results for blast excavation weight with the results from fragment size distribution analysis of all specimens, the optimal inter-hole delay was 200 µs. Compared to simultaneous detonation, the median size was decreased by about 14.5% for the inter-hole delay of 200 µs. The results of experiments show that delay time significantly influences rock fragmentation, but the stress wave superposition in short delays cannot improve rock fragmentation. For long delays, the blast-induced crack propagation time should be regarded as an influential factor when choosing the proper delay time. The experimental findings of this study could provide a better understanding of the effect of the mechanism of delay time on rock fragmentation.

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Section: Specimen and Explosivementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of the Effect of Delay Time on Rock Fragmentation in Multi-Hole Bench Blasting

Tang

Yang

2023

Applied Sciences

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“…[5] performed drop test to study the material grindability on three granites, comparing specimens blasted and not blasted; in conclusion blasting appears to reduce the work index by 5-11%. [6] conducted eight experiments on granite bench blasting models employing double holes with delay times ranging from approximately 13 ms to 300 ms, finding an "optimal" inter-hole delay at 200 µs, where to simultaneous detonation, the median size was decreased by about 14.5% for the inter-hole delay of 200 µs; the same authors in [7] conducted a similar test and found that, compared to short delay times such as 27.36 µs, x50 was improved by approximately 25% at the delay time of 180 µs. The results indicated a notable difference and substantial improvement in fragmentation when the delay times fell within the range of no-shock-wave interaction.…”

Section: Introductionmentioning

confidence: 99%

The Role of Delays in the Performance of Blasting

Seccatore,

Vigna,

Marin

et al. 2024

Preprint

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When researching rock blasting, the design parameters used for the analysis are usually the ge-ometric and charging ones. This study is based on a different approach, and focuses on the effect of timing, in specific the role of delays in the initiation sequence. The data come from the results of full-scale blasts. The experimental setting and location allowed to consider all parameter other than the number of delays as a constant. The experimental results are analyzed relating the delay var-iables to fragmentation and KPIs of downstream operations. It is shown how increasing the number of delays per unit of blasted rock and reducing simultaneous adjacent holes produces finer fragmentation, reduces the amount of fines, facilitates the secondary operations and reduces the risk of flyrock.

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“…In order to investigate the influence of delay time on rock fragmentation, Tang et al [8] conducted eight experiments employing bench blasting models with double holes. The results reported a significant difference and great improvement in fragmentation when the delay times were in the range of a no shock wave interaction compared to other interactions.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Study on the Effect of Three-Hole Simultaneous Blasting Technology on Open-Pit Mine Bench Blasting

Zhang,

Li,

Wei

et al. 2024

Applied Sciences

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Blasting technology is widely applied in various engineering applications due to its cost-effectiveness and high efficiency, such as in mining, transport infrastructure construction, and building demolition. However, the occurrence of cracking in the rear row has always been a major problem that disrupts mining bench blasting. To address this issue, a three-hole simultaneous blasting technology is proposed in this study. Both numerical simulations and onsite blasting experimental testing were conducted. To aid this endeavor, the three-hole simultaneous blasting and the hole-by-hole blasting methods were adopted to comparatively analyze the severity of the damage caused to the original rock and the effect of rock fragmentation in the rear row. The obtained results highlighted that the outcome of the blast produced by the three-hole simultaneous blasting method is satisfactory, with fewer flying stones and concentrated blasting piles required. Additionally, the original rock in the rear row showed no obvious sign of tensile damage and had uniform fragmentation. It was also found that a block size of less than 60 cm accounts for 100%, while a block size of less than 50 cm accounts for 98.7% of the whole blocks, with no large blocks reported. Moreover, a penetrating horizontal crack occurred in the direction of the connection of the blast hole center when the three-hole simultaneous blasting method was adopted. This resulted in a smooth and flat rear part of the rocks at the interface. Compared to the hole-by-hole blasting method, the three-hole simultaneous blasting method improved the effective stress and displacement at each measurement point. At the measurement point directly at the front of the borehole, the maximum effective stress attained 67.9 GPa, and the maximum displacement reported was 31.9 cm. Overall, it was shown that the three-hole simultaneous blasting technology is applicable in similar applications of mine bench blasting, which is conducive to addressing the rear row original rock strain for onsite bench blasting.

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Experimental Study on the Influence of Delay Time on Rock Fragmentation in Bench Blasting

Cited by 8 publications

References 43 publications

Experimental Investigation of the Effect of Delay Time on Rock Fragmentation in Multi-Hole Bench Blasting

Experimental Investigation of the Effect of Delay Time on Rock Fragmentation in Multi-Hole Bench Blasting

The Role of Delays in the Performance of Blasting

Experimental and Numerical Study on the Effect of Three-Hole Simultaneous Blasting Technology on Open-Pit Mine Bench Blasting

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