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1

The effect of blasting using low-density emulsion explosives

Skrlec Vinko, Dobrilovic Mario, Tumara Barbara S., Bohanek Vjecislav

Journal of Sustainable Mining

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2024

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Vol. 23, iss. 1

10--19

EN

Low-density emulsion explosives are essentially blends of an emulsion matrix and a certain amount of gaseous phase inclusions acting as hot spots. With the addition of expanded polystyrene for gaseous sensibilization, the resulting explosive blend was developed to reduce peak values and pressure impulse of gaseous detonation products on surrounding rock. This resulted in a decrease in rock stress and a decrease in cracking zone width outside of the minefield boundary. The use of low-density emulsion explosives correlates with the decrease in the seismic effect of blasting, more precisely, the decrease of induced rock oscillation velocities. The low-density emulsion explosive used in this work was validated based on laboratory and field experiments. The laboratory experiments measured dominantly detonation and safety characteristics, while field experiments characterized working capacity, i.e. single-shot blasting effect in an igneous diabase. The obtained measurements were compared against reference explosives (pentrite, emulsion explosive sensitized with glass microspheres, and ANFO explosive). Measured parameters were detonation velocity and oscillation velocity used to determine the seismic effect of blasting in the immediate borehole vicinity.

2

Estimation of active rockburst prevention effectiveness during longwall mining under disadvantageous geological and mining conditions

Wojtecki Ł., Konicek P.

Journal of Sustainable Mining

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2016

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Vol. 15, iss. 1

1--7

EN

Underground longwall mining of coal seams in the Upper Silesian Coal Basin is currently being carried out under increasingly difficult geological and mining conditions. Mining depth, dislocations and mining remnants are the main factors responsible for the most significant rockburst hazard, which can be minimized via the use of active and passive rockburst prevention. Active rockburst prevention in longwalls is usually based on blasting, in order to either destress local stress concentrations in the rock mass or to fracture the thick layers of strong roof rocks to prevent or minimize the impact of high energy tremors on excavations. The accurate estimation of active rockburst prevention effectiveness is particularly important when mining under disadvantageous geological and mining conditions, which are associated with high levels of this hazard. The efficiency of blasting applied for this purpose is typically evaluated from the seismic effect, which is calculated based on seismic monitoring data and the weight of the charged explosive. This method, as used previously in the Czech Republic, was adopted in the present study to analyze conditions occurring in a Polish hard coal mine in the Upper Silesian Coal Basin. Parameters of long hole destress blastings in roof rocks (torpedo blastings) from the face of the assigned longwall in coal seam no. 507 were correct a success according to the seismic effect method and corresponded to observations made in situ. The analytical method presented enables the rapid estimation of destress blasting effectiveness and could also be useful when determining appropriate active rockburst prevention.

3

Milisekundowe odpalanie ładunków a efekt sejsmiczny strzelania w kopalniach odkrywkowych

Onderka Z.

WUG : bezpieczeństwo pracy i ochrona środowiska w górnictwie

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2003

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nr 7

15-17

PL

Odpalanie milisekundowe ładunków MW może wpływać na zmniejszenie intensywności drgań parasejsmicznych pod warunkiem doboru odpowiedniego opóźnienia międzystrzałowego. Problemem ciągle jest wpływ liczy ładunków odpalanych milisekundowo na wielkość drgań, a więc dopuszczalna wielkość ładunków w serii otworów. W artykule zaproponowano odpowiedni sposób, który może być uzupełnieniem stosownych przepisów dotyczących wyznaczania stref zagrożenia przy strzelaniu.

EN

The millisecond firing of explosive charges may influence the para-seismic vibrations to the effect of reducing their intensity level, under the condition of choosing the right inter-blasting delay. Instead, still remains the problem of the effect of the number of explosive charges fired under a millisecond-delay system on the magnitude of vibrations, that is the permissible amount of explosive charge in a series of blast holes. Proposed in the article has been an appropriate procedure which may serve as a supplement to the relevant regulations pertaining to determination of hazard in blasting work.