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Purpose The purpose of this paper is to investigate the applicability of the LS-DYNA software using a Lagrangian formulation in the jet formation, flight and penetration of improvised explosively formed projectiles (EFPs). Numerical results dealing with different properties of the EFPs have been validated with a significant number of field tests. Design/methodology/approach 2D and 3D Lagrangian models, using different material definition, are developed to reproduce the field-measured characteristics of copper- and steel-made EFPs: projectile size and velocity. After validation, the model has been extended to analyse the penetration features. Two different plasticity models have been used to describe the steel target, Plastic-Kinematic and Johnson–Cook. Findings Despite the difficulty in characterizing a non-industrial artefact, the results show that both Lagrangian models (2D and 3D) are able to simulate the projectile size, velocity and penetration capability with errors less than 10 per cent when using the Johnson–Cook material model for both liner and target. Practical implications These data can be used to test the penetration ability of improvised EFP’s against different targets, i.e. light armoured vehicles. Originality/value There are no references that address the application of the Lagrangian simulation of non-industrial EFPs and its validation with field tests, including penetration assessment.

Mining represents the first step to the access to mineral resources. The impacts induced by such operations now contribute to the impacts of a wide range of goods and services, given the widespread use of these raw materials in the worldwide economy. In this context, this study aims at assessing the environmental performance of mining operations in a life cycle perspective, considering two currently operating mine sites: the Erzberg iron open-pit mine (Austria) and the Lujar fluorspar underground mine (Spain). In particular, this study aims at i) identifying the main environmental hotspots along the cradle-to-gate exploitation of mineral deposits in these two mines (“reference scenarios”), ii) assessing the environmental performance of two alternative mining solutions (“alternative scenarios”), respectively the use of alternative explosive compositions (including their associated air emissions) and the implementation of a new blast design method. This assessment relies on representative sets of data primarily drawn from on-site operations and experimental results, completed with other data sources to fill the gaps. The environmental impacts are characterized based on the European EF (Environmental Footprint) life cycle impact assessment method. Firstly, among the 16 impact categories considered, the production of 1 ton of iron concentrate (33.5% Fe) in the Erzberg mine in particular potentially induces a total of 8.75 kg CO2-eq. The consumption of ferrosilicon in the concentration step (main contributor to 8 impact categories out of 16), of steel in the comminution step (main contributor to 2 impact categories), and of diesel by the machinery necessary for loading/hauling the ore (main contributor to 3 impact categories) stand for the main environmental hotspots in the Erzberg case. Secondly, the production of 1 ton of fluorspar concentrate (79.2% CaF2) in the Lujar mine potentially induces a total of 174 kg CO2-eq. The consumption of diesel by the machinery and the on-site generators in the mining and loading/hauling steps (main contributor to 11 impact categories out of 16), along with the mine infrastructure/equipment (main contributor to 4 impact categories) are identified as the main environmental hotspots in the Lujar case. The implementation of both alternative mining solutions results in relatively limited environmental effects on the overall life cycle environmental performance of the Erzberg mining operations (less than 3% difference in terms of impacts). Finally, this study highlights that some challenges still remain to be addressed in order to better secure the use of life cycle assessment in the mining context, in particular in terms of data monitoring/measurement or impact assessment methods.

In order to clarify the requirements for satisfactory coupling on rock, six methods to monitor vibrations with blasting seismographs are investigated in the longitudinal component of the vibratory motion. The methods studied consisted on placing the geophone mount on a granite surface freely (loosely), held with a sandbag, and attached with an anchor (the center of the geophone's mount was fixed with a plastic anchor, a bolt and a nut), thermal adhesive (glue), gypsum plaster (used as an adhesive) and double-sided tape. For each measuring condition, transmissibility in two mounts was assessed on a vibration shaker from 2 to 190 Hz at one or two vibration levels (5, 20 mm/s). The main findings of this work are: (1) Transmissibility varies with coupling method. It is flat at low frequencies and has a maximum at higher frequencies; in some trials mainly with anchored, glued and plastered such peak occurs outside the frequency range studied. (2) The frequency of the first maximum of transmissibility shifts towards smaller frequencies as the peak velocity increases when the bonding conditions are weak, as for free and sandbagged mounts. However, if the bonding is stiff enough, as for anchored or plastered mounts, transmissibility values at 5 and 20 mm/s are very similar. (3) The frequency of the first peak in the measured transmissibility provides a preliminary estimate of the performance of each method, so that its conditions of use should be defined upon frequency and velocity of the imposed motion, rather than using the anticipated peak acceleration, as it is currently made. These have been defined for the methods under study. (4) Anchoring and plastering provide the best performance, the later with smaller errors at high frequencies (>128 Hz). (5) The seismograph itself (not the coupling) is another source of error that should not be neglected specially for measurements in the low frequency range; large errors, exceeding by one order of magnitude those from coupling are obtained in the 2‒4 Hz band.

A damage assessment methodology, based on the Schmidt hammer rebound value, has been developed and applied to evaluate the integrity of different structural elements after a blast event. All the elements (nine slabs, five beams and four masonry walls) were tested at full-scale with scaled distances that range from 0.2 to 2.92 m/kg1/3. The methodology consists of the evaluation of a statistically significant difference between six rebound values before and six after a blast event at each evaluation point. Based on each individual damage value, damage maps have been created using an interpolation tool. The combination of a global damage value with the spalled area based on visual inspection, allows the comparison between different protective solutions against blasting. The methodology presented and validated in this work can be used to evaluate the status of different concrete elements after a blast event such as terrorist attacks and can be also used for determination of the quality of different protective solutions. In terms of the solutions tested, the use of fibers enhances the tensile resistance of specimens. Concrete in beams configuration appears to have less resistance than in slabs, making them more vulnerable against explosives. To reduce the inner spalling in tiling wall areas, and the associated injuries, a good potential solution is the basalt fiber mesh.

This paper investigates the advantages and accuracy of a finite element simulation of a blast loaded full-scale slab by validating the results with the corresponding field tests. For this modeling, a 3D pure Lagrangian approach using LS-DYNA with appropriate blast load routine (CONWEP), material models and suitable boundary conditions is developed. Eight full-scale slabs were cast and tested. Three standard reinforced concrete slabs with the explosive at a scaled distance of 0.79 m/kg1/3 were used to calibrate the numerical model. Two normal reinforced concrete (RC) slabs with the explosive charges located at scaled distances of 0.41 and 0.20 m/kg1/3, and three more with different constructive solutions, such as fiber reinforced concrete (steel and polypropylene fibers) or reinforced concrete protected with a steel sheet at the center of the slab, aim to study the sensitivity of the model to these changes. Field data obtained with accelerometers and pressure transducers are compared with results obtained from the numerical modeling for the calibration tests. For the others, the results from numerical model match those from field blast tests in terms of damage pattern and percentage of surface damage. The model is sensitive to the effect of scaled distance (explosive at lower scaled distance produced higher surface damage and different fracture patterns) and to different construction patterns. Reinforced concrete slabs with steel or polypropylene fibers had better blast resistance under tensile stress (bottom part of the slabs) than simple reinforced concrete. The slab with the steel sheet on top had higher surface damage on both faces than the others for the same scaled distance.

Field guidelines and recommendations for blasting vibration monitoring on a hard surface, suggest that the geophone mount should be coupled to the ground in a way that depends on the anticipated vibration level. However, the quantitative performance of the coupling method is basically unknown. In order to investigate this, the ground-to-mount coupling transmissibility (i.e. ratio of the response of the geophones mount to the rock motion, as a function of frequency) was measured between 16 and 200 Hz in 43 tests using a vibration exciter. The geophone mounts were freely placed, hold with a sandbag and anchored on granite. Free placed mounts applied outside the suggested range of vibrations (i.e. frequencies above 50–70 Hz at 5 mm/s) lead to the largest expected errors (up to 7.5 dB). Distortion is still significant (1.02 dB), though to a minor degree, at lower levels where this method is recommended. Sandbagging limits the maximum expected error to 1.6 dB, but it is ranked as the worst method irrespective of the vibration level and the sandbag planting at frequencies below 40 Hz. Anchoring appears as the only analyzed method that achieves a stiff rock-to-mount coupling, ensuring consistent measurements for the frequencies commonly found in blasting independently of the vibration level and the mount characteristics.

This paper investigates the propagation of airblast or pressure waves in air produced by bench blasting (i.e. detonation of the explosive in a row of blastholes, breaking the burden of rock towards the free vertical face of the block). Peak overpressure is calculated as a function of blasting parameters (explosive mass per delay and velocity at which the detonation sequence proceeds along the bench) and the polar coordinates of the position of interest (distance to the source and azimuth with respect to the free face). The model has been fitted to empirical data using linear least squares. The data set is composed of 122 airblast records monitored at distances less than 400 m in 41 production blasts carried out in two quarries. The model is statistically significant and has a determination coefficient of 0.87. The formula is validated from 12 airblast measurements gathered in five additional blasts.

A model for the calculation of the productivity of cyclic excavators is developed. The production rate results as a product of an ideal, maximum, productivity rate (one of the coefficients of the model) times an operating efficiency. The latter is described as a function of three variables (rock strength, nominal bucket capacity and explosive energy concentration) and three more coefficients. The coefficients of the model have been obtained from field measurements in twenty production blasts at two open pit mines, for which mechanical properties of the rock, blasting characteristics and mucking rates were carefully measured. The model is statistically significant and explains up to 90 % of the variance of the production rate measurements.