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 blast-induced 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.
22 February 2022 in Journal of Rock Mechanics and Geotechnical Engineering
Ammonium nitrate fuel oil (ANFO) samples, which were obtained by blending two different types of ammonium nitrate porous prills (i.e., AN-PP7 and AN-PP8) with fuel oil (FO) were studied. Measurements of structure, crystallinity and morphology were performed using X-ray Diffraction (XRD), Infrared Spectroscopy (IR) and Scanning Electron Microscopy (SEM), respectively. From the SEM analysis, it was indicated that a “wrinkled” structure characterized the crystal surface of the samples, which were based on two types of ammonium nitrate porous prill. Thermogravimetric analysis and differential scanning calorimetry (TGA/DSC) confirmed that AN-PP7 had a higher absorption index in comparison to AN-PP8. Furthermore, it was shown that continuous AN phase transformations at precise temperatures took place. From the blasting test, it was indicated that the absorption index only had an influence on the content of toxic fumes. However, the velocity of detonation (VOD) depended solely on the ANFO density as well as the total volume of post-blast fumes.
Non-ideal explosives with differing contents of silicon dioxide (silica or dioxosilane) added in the form of powder and gel were tested. Measurements of structure, crystallinity and morphology were performed by means of infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). IR and XRD analysis revealed a lack of SiO2 influence on the non-ideal explosive structure. SEM analysis indicated that all the surface deformations of ammonium nitrate(V) prill were filled by a thin fuel film layer on which SiO2 was present. The additional calculations of selected theoretical properties of non-ideal compositions were made using ZMWCyw software. Based on this, it was established that the optimum semimetal content was 1.0 wt.%. Blasting tests confirmed that the addition of 1.0 wt.% SiO2 to the Ammonium Nitrate Fuel Oil (ANFO) resulted in the lowest volume of post-blast fumes. Moreover, it was established that finer SiO2 powder cannot be used as the oxide component enhancer due to the inhibition of detonation reaction. SiO2 should be used only as an inert component.
The verification of the blasting parameters of Ammonium Nitrate Fuel Oil (ANFO) with the addition of microstructured charcoal (MC) produced by destructive wood distillation was performed. Additional investigation of specific surface and pore distribution by the nitrogen adsorption of the two granulations of MC was also carried out. High-resolution scanning electron microscopy was used for morphology evaluation and revealed smoothening of the initially developed external surface of carbon with intensive milling. In addition, the analysis of the thermal properties of the studied samples (TG/DSC) indicated that the size of the microstructured charcoal additives influenced the decomposition temperature of the prepared materials. The explosives containing microstructured charcoal grains of −90 μm underwent decomposition at lower temperatures in comparison with those containing higher sizes of microstructure charcoal grains (−1.18 mm), for which the decomposition temperature reached 292 °C. The obtained results of blasting parameters compared to the results derived from thermodynamic simulation showed the non-ideal character of the explosives (much lower values of blasting parameters than in established thermodynamic models). It was indicated that higher velocities of detonations (VOD) were obtained for non-ideal explosives where finer MC grains were added. Blasting tests confirmed that the studied type of MC can be applied as an additive to the ANFO.