Abstract
The emission of dust particles into the atmosphere during rock mass breaking by blasting in ore mining open-pits is one of the factors that determine the ground-level air pollution in the vicinity of pits. The data on dust concentration in the cloud, which is extremely difficult to obtain experimentally for large-scale explosions, is required to calculate the dust dispersion in the wind stream. We have elaborated a Eulerian model to simulate the initial stage of dust cloud formation and rising, and a Navier–Stokes model to simulate thermal rising and mixing with the ambient air. The first model is used to describe the dust cloud formation after a 500 t TNT (Trinitrotoluene equivalent) explosion. The second model based on the Large Eddy Simulation (LES) method is used to predict the height of cloud rising, its mass, and the evolution of dust particles size distribution for explosions of 1–1000 t TNT. It was found that the value of the turbulent eddy viscosity coefficient (Smagorinsky coefficient) depends on both the charge mass and the spatial resolution (grid cell size). The values of the Smagorinsky coefficient were found for charges with a mass of 1–1000 t using a specific grid.
Highlights
It is estimated that from hundreds of billions to a trillion t of solid substance are extracted from the lithosphere each year
The main parameters of these data include the dust cloud height, horizontal dimension of the dust cap, the dust mass contained in the cloud cap, and distribution of the dust mass by the particle size
The initial gas and dust cloud are formed near the ground surface after the expansion of detonation wave, dust ejection from the crater, and mixing the dust and detonation products with the ambient air
Summary
It is estimated that from hundreds of billions to a trillion t of solid substance are extracted from the lithosphere each year. Despite the wide use of large-scale blasting during development of mineral deposits, using open-pit mining, the emission of particulate pollutants into the atmosphere induced by explosions has not been sufficiently studied yet. This is due to a lack of data and unreliability of available tests [20]. The formation of a hot cloud filled with detonation products, air and dust in the vicinity of the explosion epicenter, and the subsequent convective rise of hot gas and dust cloud in the stratified atmosphere are ignored in such models These processes become crucial for dust transfer generated by powerful large-scale (>1 t TNT) explosions. Some conclusions and discussions are presented in the last section
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