Fracture Initiation, Gas Ejection, and Strain Waves Measured on Specimen Surfaces in Model Rock Blasting

Zhang, Zong-Xian; Li, Yuan; Qiao, Yang; Hou, De-Feng

doi:10.1007/s00603-020-02300-2

Cited by 19 publications

(6 citation statements)

References 30 publications

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“…In addition, Fourney (2015) showed that the S-wave induced by the reflection of the compressive wave at the free surface might cause cracks in the radial direction of a blast model. Interestingly, in model blasting (Chi et al 2019a;Zhang et al 2021a), some radial cracks were discovered on the free surfaces of the rock specimens, but no gas was ejected out of such radial cracks, meaning that these radial cracks were initiated from the free surfaces rather than from the blastholes. This is consistent with the analysis by Fourney (2015) to a certain extent.…”

Section: Free Surface and Barrier Nearbymentioning

confidence: 99%

Reduction of Fragment Size from Mining to Mineral Processing: A Review

et al. 2022

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The worldwide mining industry consumes a vast amount of energy in reduction of fragment size from mining to mineral processing with an extremely low-energy efficiency, particularly in ore crushing and grinding. Regarding such a situation, this article describes the effects of rock fragmentation by blasting on the energy consumption, productivity, minerals' recovery, operational costs in the whole size reduction chain from mining to mineral processing, and the sustainability of mining industry. The main factors that influence rock fragmentation are analysed such as explosive, initiator, rock, and energy distribution including blast design, and the models for predicting rock fragmentation are briefly introduced. In addition, two important issues-fines and ore blending-are shortly presented. Furthermore, the feasibility of achieving an optimum fragmentation (satisfied by a minimum cost from drilling-blasting to crushing-grinding, maximum ore recovery ratio, high productivity, and minimum negative impact on safety and environment) is analysed. The analysis indicates that this feasibility is high. Finally, the measures and challenges for achieving optimum fragmentation are discussed. Highlights• The effects of rock fragmentation on the whole size reduction chain from mining to mineral processing are described.• The main factors influencing rock fragmentation by blasting are analysed.• Main models for predicting rock fragmentation are briefly introduced and commented on.• The feasibility, measures, and challenges of achieving optimum fragmentation are analysed.

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Section: Free Surface and Barrier Nearbymentioning

confidence: 99%

Reduction of Fragment Size from Mining to Mineral Processing: A Review

et al. 2022

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“…Fractured zone was contribute to main part of rock fragmentation by blasting in engineering, the failure range of which was much larger than that of crushed zone. The length, velocity of crack and damage range in fractured zone played an important role in determining delay time, designing a blast and understanding the mechanism of rock fragmentation by blasting [30]. Therefore, the influences of initial stress on crack length, crack velocity, and damage range were analyzed in detail in the following sections.…”

Section: Effect Of Initial Stress On Crack Propagation In Fractured Zonementioning

confidence: 99%

Test and mechanism analysis for crack propagation by blasting in rock under the condition of unidirectional load

Ge¹,

Xu²

2022

J. vibroeng.

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In deep rock blasting, there are different constraint conditions such as unidirectional loading, bidirectional loading and tridirectional loading due to in-situ stress. The similar model test of rock blasting under unidirectional load was carry out to study the law of crack propagation in rock by blasting in this study. A transparent material which conformed to the mechanical properties of hard rock is used to make specimens. A high-speed camera was used in some model blasts. After blasting the surface cracks on the specimen were measured, including the near zone and middle zone of blasting. The results showed that: (1) the radial main cracks in the specimens under initial static load propagated along the principal stress direction, which is different from that without initial stress, and there is almost no radial main crack in the direction perpendicular to the principal stress. (2) The average length of radial crack and diameter of circumferential fracture circle gradually decrease with the increase of unidirectional initial stress, but the diameter of compression crushing circle increase. (3) The maximum and average initial velocity of radial crack growth decrease with the increase of unidirectional initial stress.

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“…In addition, it can be found that each of the three energies varies over a large range since energy efficiency is affected by many factors such as burden, spacing, confinement, delay time, charge parameters, initiation, and the like. For example, model blasts indicated that: (1) stemming conditions affected the initiation of gas ejection out of blastholes (Zhang et al 2021); (2) unstemmed holes wasted 25% of the explosive energy (Zhang et al 2020a) available for rock fragmentation, compared with partially-stemmed blasts; (3) the specific charge influenced the crack propagation velocity (Chi et al 2019b). In addition, field measurements by Brinkmann (1990) indicated that unstemmed blastholes in underground mining blasts wasted 50% of the explosive energy in the form of 'leaking' gases, compared with fully-stemmed blastholes.…”

Section: Energy Components In Rock Blastingmentioning

confidence: 99%

Energy Requirement for Rock Breakage in Laboratory Experiments and Engineering Operations: A Review

Zhang

Ouchterlony

2021

Rock Mech Rock Eng

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Based on the review of a wide range of literature, this paper finds that: (1) the average specific surface energy of various single crystals is only 0.8 J/m2. (2) The average specific fracture energy of the rocks with a pre-crack under static cleavage tests is 4.6 J/m2. (3) The average specific fracture energy of the rocks with a pre-cut notch but with no pre-crack under static tensile fracture (mode I) tests is 4.6 J/m2. (4) The average specific fracture energies of regular rock specimens with neither pre-made crack nor pre-cut notch are 26.6, 13.9 and 25.7 J/m2 under uniaxial compression, tension and shear tests, respectively. (5) The average specific fracture energy of irregular single quartz particles under uniaxial compression is 13.8 J/m2. (6) The average specific fracture energy of particle beds under drop weight tests is 74.0 J/m2. (7) The average specific fracture energy of multi-particles in milling tests is 72.5 J/m2. (8) The average specific energy of rocks in percussive drilling is 399 J/m3, that in full-scale cutting is 131 J/m3, and that in rotary drilling is 157 J/m3. (9) The average energy efficiency of milling is only 1.10%. (10) The accurate measurements of specific fracture energy in blasting are too few to draw reliable conclusions. In the last part of the paper, the effects of inter-granular displacement, loading rate, confining pressure, surface area measurement, premade crack, attrition and thermal energy on the specific fracture energy of rock are discussed.

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Fracture Initiation, Gas Ejection, and Strain Waves Measured on Specimen Surfaces in Model Rock Blasting

Cited by 19 publications

References 30 publications

Reduction of Fragment Size from Mining to Mineral Processing: A Review

Reduction of Fragment Size from Mining to Mineral Processing: A Review

Test and mechanism analysis for crack propagation by blasting in rock under the condition of unidirectional load

Energy Requirement for Rock Breakage in Laboratory Experiments and Engineering Operations: A Review

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