Modelling the influence of gaseous products of explosive detonation on the processes of crack treatment while rock blasting

Purpose is mathematical modeling of fracturing as well as influence of gaseous products of explosive detonation on the changes in rock strength. Methods. Mathematical model, using foundations of Griffith theory, has been developed. To explain conditions of bridge formation while exploding lead azide charges, a two-stage description of solid particle condensation at a crack surface and inside it has been applied using the smoothed particle hydrodynamics. The analysis, involved electronic microscope, has helped verified the results experimentally. Findings. The effect of rock mass disturbance, resulting from explosive destruction, is manifested maximally right after the action. Subsequently, it decreases owing to the gradual relaxation of the formed defects. Therefore, an urgent problem is to develop ways slowing down strength restore of the blasted rock mass fragments. The process of rock fragment strength restoring may be prevented by microparticles getting into the microcrack cavities together with the detonation products. The research simulates their action. The data correlate to the simulation results confirming potential influence of the blasted rock on the dynamics of changes in the strength characteristics of the rock mass. Various compositions of charges with shells made of inert solid additions have been applied which solid particles can avoid the process of microcrack closure. Originality. For the first time, the possibility of deposition formation within rock micro- and macrocracks has been proposed and supported mathematically. Practical implications. Strength properties of the finished product and the energy consumption during impulse loading as well as subsequent mechanical processing of nonmetallic building materials depend on the strength properties of rock mass fragments. Hence, the ability to control the strength restore has a great practical value. Moreover, it can be implemented during the blasting operations.

Fabrication of Nanoscale Homogeneous Lead Azide@Carbon Fiber Film with Low Electrostatic Sensitivity by In-situ Synthesis

In this work, a nano-scale carbon-based lead azide initiating film was prepared by electrospinning, carbonization, azide, and other steps using cheap and easily available lead acetate as the raw material....

Modern Trends in “Green” Primary Energetic Materials

The evergrowing demand for cleaner, high-performing energetic materials (EMs) has led to a quest for replacement of currently used toxic metal-based traditional energetic compounds such as lead azide and lead...

Experimental Study on Blasting Energy Distribution and Utilization Efficiency Using Water Jet Test

The blasting stress wave and blasting gas generated by explosive blasting are the two main motive powers of rock fragmentation. An experimental method based on water jet test is used to study the energy distribution ratio of blasting stress wave and blasting gas; the utilization efficiency of blasting energy under different borehole constraint conditions is also analyzed. It proves that the blasting stress wave does not cause the water jet, and the blasting gas is the only power of the water column jet. The results show that the energy of the blasting gas and blasting stress wave respectively account for about 64% and 36% of the total energy generated by the explosion of lead azide. The utilization efficiency of the blasting gas energy under strong, medium, and weak constraint conditions is 100%, 80%, and 52%, respectively. The borehole constraint condition is crucial for the effective utilization of blasting energy.

On improving the efficiency of blasting operations in underground and open-pit mining

The purpose is to study the effect of microstructure defects of initiating explosives on the process of initiating detonation by a laser monopulse. The results of experimental studies and physico-mathematical modeling of the effect of microstructural defects in crystals of photosensitive initiating explosives under the action of a single laser pulse are given. The paper covers a brief analysis of the history of the issue being studied and physico-mathematical modeling using the theory of elastic scattering, i.e. Gustav Mie theory. The technique for determining the absorption cross section of laser radiation by micro-sized inclusions of explosive has been developed and tested. In experiments on explosives ignition using a laser monopulse, the laser monopulse shape was recorded, the energy distribution over the laser beam radius and the explosive ignition delay time were controlled. The basis is the proposed method of calculating the absorption cross section and intensity in terms of the laser radiation wavelength by the inclusion of an explosive with using the theory of elastic scattering of optical radiation on particles in micrometer size range. It is shown that the absorption properties of the particle essentially depend on the properties of the particle medium and the wavelength of radiation. For smoke particle within PETN the absorption for wavelength of laser radiation of 1.06 μm is stronger than for that of 0.69 μm. A different absorption occurs if a lead particle is within a lead azide: absorption for wavelength of 0.69 μm is twice as strong as for wavelength of 1.06 μm. During the manufacture of explosives the additional defects in the explosives microstructure are desired to be created to increase the efficiency of laser initiation. Findings are used in the development of technical specifications for the design of optical detonators for laser initiation systems.

Features of initiating the light-sensitive explosive composites for safe blasting of borehole charges in coal mines

The purpose of paper is to study physical and chemical patterns for starting detonation in the explosive charges by means of laser pulse radiation. Studies of the physical and chemical properties of the mechanism for stimulating the detonation of explosives by pulse radiation of an optical quantum generator have been carried out. Methodology of experimental and theoretical studies as well as mathematical modeling, involving gas-dynamics equations, has been applied. Basic research results as for studying sensitivity of the explosives being initiated by pulse light radiation have been analyzed. Numerical modeling was performed taking into consideration the real process of igniting the explosive by infrared laser radiation. The proposed mathematical model makes it possible to study the peculiarities of initiating the explosive transformation of bursting explosives by means of short light pulses. Tetranitropentaerytrite (PETN) was used to show that the process is determined completely by the parameters which characterize radiation intensity and absorption properties of the explosive. Depending on these parameters values, initiation processes may be implemented qualitatively – either on the surface or inside the explosive. In the latter case, the release of chemical energy results in the formation of so-called “chemical” pressure peak. With the use of lead azide, it has been shown experimentally that the initial temperature does not affect the increase in explosive sensitivity even in case when laser radiation takes place in the nanosecond pulse mode. Experimental results are applied while developing light-sensitive composites with the preset explosive and physical-chemical properties. The determined patterns were used in the development of the light-sensitive explosive composites for blasting agents of explosive charges.