Numerical modelling for blast-induced fragmentation in sublevel caving mines

Yi, Changping; Sjöberg, Jonny; Johansson, Daniel

doi:10.1016/j.tust.2017.05.030

Cited by 75 publications

(21 citation statements)

References 5 publications

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“…Yi et al [ 20 ] constructed a four-hole model to study the impact of short delays on rock fragmentation and indicated that increased fragmentation was found for longer delays (3 ms and 6 ms) compared with simultaneous initiation and 1ms delay. Similar simulations in sublevel caving by Yi et al [ 21 ] showed that the 2 ms case gave a finer fragmentation than the 0 ms and 1 ms cases. The existence of the stress wave superposition in short delay blasting was also questioned by some researchers.…”

Section: Introductionsupporting

confidence: 58%

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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Section: Introductionsupporting

confidence: 58%

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

et al. 2018

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“…The model has some limitations in that the crushed zone is axisymmetric, does not include shear response or rotational degrees of freedom, and the in situ stress is constant though produced median fragment sizes similar to those predicted using a Kuz-Ram approach. Modelling was done with the transient dynamic elasto-plastic 3D LS-DYNA finite element package (Yi et al 2017). It is not possible to explicitly create blast-induced fragmentation finite element models so a geometric approach is used to identify the formation of 3D blocks.…”

Section: Blast Design Approachesmentioning

confidence: 99%

Breaking new ground: challenges and opportunities for maximising value from underground blasting

Sellers¹,

Salmi²

2020

Proceedings of the Second International Conference on Underground Mining Technology

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The challenges of underground mining operations have discouraged mine-to-mill value optimisation to maximise metal production by tailoring fragmentation for plant throughput. Improved and automated blasting techniques are required for modern remote, deeper, and highly stressed operations. The definition of value is changing with investors seeking environmental, social, and governance measures, as well as the traditional revenue and net present value approaches. In this paper, analyses of blasting from a range of underground operations are used to highlight the current challenges. Demonstration of how the lack of sufficient and appropriate continuous, 3D measurement of important properties such as blastability, in situ structures, hole deviation, and fragmentation aligned with the limited insights into the effect of mining-induced stresses show how current approaches can often lead to overbreak, dilution, production delays, the lack of excavation stability, and poor plant performance. The real-time fusion of data to recalibrate and monitor the continuously changing environment is required. On the horizon, there is a suite of new technologies such as wireless detonators, nitrate-free explosives, robotic operations, and cognitive spatial management that will enable a new generation of mining methods. These include in-place operations and in-mine recovery where the material movement and the environmental footprint of mining operations is reduced whilst extraction is optimised, and productivity and excavation stability increased.

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“…Several models are available for the response of brittle materials, especially rock. The most commonly used are the Johnson-Holmquist Concrete model (JHC model; sometimes referred to as the Holmquist-Johnson-Cook model) [36,37], the brittle damage model [22,38], the Federal Highway Administration (FHWA) soil model [13,39], the Riedel-Hiermaier-Thoma (RHT) model [3,40], the Continuous Surface Cap (CAP) model [38,41], and the Karagozian and Case Concrete (KCC) model [42,43]. Among constitutive models, the Johnson-Holmquist II (JH-2) model has been extensively used to reproduce the behavior of brittle and geomaterials under dynamic or impact loading conditions [15,18,[44][45][46][47][48][49][50][51].…”

Section: Introductionmentioning

confidence: 99%

Experimental testing and numerical simulations of blast-induced fracture of dolomite rock

et al. 2020

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In this paper, the Johnson-Holmquist II (JH-2) model with parameters for a dolomite rock was used for simulating rock fragmentation. The numerical simulations were followed by experimental tests. Blast holes were drilled in two different samples of the dolomite, and an emulsion high explosive was inserted. The first sample was used to measure acceleration histories, and the cracking pattern was analyzed to perform a detailed study of the blastinduced fracture to validate the proposed method of modelling and to analyze the capability of the JH-2 model for the dolomite. The second sample was used for further validation by scanning the fragments obtained after blasting. The geometries of the fragments were compared with numerical simulations to further validate the proposed method of modelling and the implemented material model. The outcomes are promising, and further study is planned for simulating and optimizing parallel cut-hole blasting.

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Numerical modelling for blast-induced fragmentation in sublevel caving mines

Cited by 75 publications

References 5 publications

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

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

Breaking new ground: challenges and opportunities for maximising value from underground blasting

Experimental testing and numerical simulations of blast-induced fracture of dolomite rock

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