Abstract
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.
Highlights
The majority of engineering and building materials are of heterogeneous structure; they contain many defects of crystal lattice, microcracks, and foreign inclusions with different physicomechanical and physicochemical properties
To explain the conditions of deposit formation during the model blasting by means of lead azide charges, a description of condensation mechanism of solid particles at the surface of crack and inside them was applied using a two-stage approach of the smoothed particle hydrodynamics (SPH) [9]-[11]
The following was assumed while selecting the theoretical model [12], [13]: 1) lead azide purity is 96%; 2) the charge is of spherical shape; initiation takes place in the central share of the sphere; and a massless single particle acts as an initiator; 3) detonation is followed by the reactions: Pb(N3)2 → Pb + N3 N3 → N2 + N
Summary
The initial stage of the research involved the development of a mathematical model based upon Griffith theory foundations. To explain the conditions of deposit formation during the model blasting by means of lead azide charges, a description of condensation mechanism of solid particles at the surface of crack and inside them was applied using a two-stage approach of the smoothed particle hydrodynamics (SPH) [9]-[11]. Stage one of the experiment simulated lead azide (LA) molecularly using (7·10-4 m) particles. When a non-destructive explosive charge containing fine dust as a shell was blasted, the model was divided into parts using a metal wedge; the fracture surfaces were analyzed with the help of an electron microscope
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