DEVELOPMENT OF THE MECHANISM OF ACTION OF DECONCENTRATED CHARGES OF VARIOUS SHAPES FOR VARIOUS MINING CONDITIONS

The modern requirements of the market economy and the increasing complexity of the field development conditions require new scientific and technical approaches in deep quarries and mines in the complex development of subsurface resources. As you know, the dominant mining paradigm in drilling and blasting is associated with the technique of drilling wells and boreholes of a circular shape (cavity) with the placement of explosives in it. However, in mining science and practice, the variety of mining conditions has long required the creation of methods for the destruction of rocks with an asymmetry in the distribution of explosion energy in space and its maximum concentration in certain directions. In this regard, we consider a conceptual direction based on a fundamentally new mechanism of action of the explosion of known groups of parallel-converged borehole charges, which effectively expand their use in various mining applications. The development of a new mechanism of action of the explosive process with the use of a computer program and numerical simulation of calculations made it possible to use the change in the shape and design of the charge as a means of increasing the share of the energy flow of the explosive explosion in a certain direction. The design of the deconcentrated charge is shown as a means of increasing the fraction of the energy flow of the explosive explosion in a given direction, which leads to a significant increase in the efficiency of the directed explosion and, in particular, minimizes its action in the opposite," legit", direction. Based on the results of the research, a method of blasting operations is proposed to neutralize the influence of anomalies in the state of the massif on mining operations by the explosive method. The method includes the appropriate tools, characterized by an unconventional design of the borehole charge and using a mechanism for influencing the anomalous states of the array with a combination of its explosive features.

Low-Energy Fragmentation Dynamics at Copahue Volcano (Argentina) as Revealed by an Infrasonic Array and Ash Characteristics

Ash-rich eruptions represent a serious risk to the population living nearby as well as at thousands of kilometers from a volcano. Volcanic ash is the result of extensive magma fragmentation during an eruption, and it depends upon a combination of magma properties such as rheology, vesicularity and permeability, gas overpressure and the possible involvement of external fluids during magma ascent. The explosive process generates infrasonic waves which are directly linked to the outflow of the gas-particle mixture in the atmosphere. The higher the overpressure in the magma, the higher should be the exit velocity of the ejected material and the acoustic pressure related to this process. During violent eruptions, fragmentation becomes more efficient and is responsible for the extensive production of ash which is dispersed in the atmosphere. We show that the phase of intense ash emission that occurred during March 2016 at Copahue volcano (Argentina) generated a very low (0.1 Pa) infrasonic amplitude at 13 km, raising a number of questions concerning the links among acoustic pressure, gas overpressure and efficiency of magma fragmentation. Infrasound and direct observations of the eruptive plume indicate that the large quantity of ash erupted at Copahue was ejected with a low exit velocity. Thus, it was associated with eruptive dynamics driven by a low magma overpressure. This is more evident when infrasonic activity at Copahue is compared to the moderate explosive activity of Villarrica (Chile), recorded by the same array, at a distance of 193 km. Our data suggest a process of rigid fragmentation under a low magma overpressure which was nearly completely dissipated during the passage of the erupting mixture through the granular, ash-bearing crater infilling. We conclude that ash released into the atmosphere during low-energy fragmentation dynamics can be difficult to monitor, with direct consequences for the assessment of the related hazard and management of eruptive crises.

Virtual ignition of a methane leak by electric spark

In the virtual environment, respectively in a rectangular tube with a hole at one end, a computational simulation was performed comprising two stages: the first stage aims at simulating a methane gas leak through a hole in the floor of the tube and its diffusion in the air of which the inner volume of the virtual environment is constituted. At the full end of the tube is arranged an electric ignition source that activates in parallel with the gas source, being observed the formation of the explosive mixture in the proximity of the ignition source and the moment of initiation of the explosive atmosphere. The second stage of the simulation is marked by a higher level of velocities characteristic of the explosive process of the airmethane mixture, which involves the use of different settings. The host of the computer simulation is the Fluent application of the ANSYS platform. Post-processing is performed both on the ANSYS platform, through the Fluent and Results applications and through the facilities offered by the Tecplot 360 application.

Estimating the amplitude of the pressure on the obstacle of products of an under-compressed outgoing detonation wave of a structured charge

The study relies on the concepts of various mechanisms of explosives decomposition at supersonic propagation of the under-compressed detonation reaction zones, and examines the structured charges explosion effect on compressible obstacles. In such charges, artificially or naturally, there can appear rod-like formations highly capable of detonation, penetrating the charge and ensuring the propagation of the complete heat release zone at a speed greater than the normal, and the ideal detonation speed of a monodisperse charge is of the same density. We introduce a simple algebraic model of the explosive process of structured charges, the process proceeding in the form of under-compressed detonation. We obtained algebraic expressions that make it possible to compare the peak pressures at the obstacles depending on the direction of detonation propagation relative to the obstacle and on the mode of detonation, i.e. whether it is normal or “under-compressed”.

Modelling of an explosion impact on a deformable medium with rigid inclusions with quasiconformal mappings methods

The explosive process influence on the environment with the existing impenetrable fixed inclusion is investigated by quasiconformal mappings numerical methods and step-by-step parameterization of the environment and the process characteristics numerical methods. The boundaries of the crater formed by the explosion, pressed and undisturbed areas of soil are determined. Numerical experiments were performed on the basis of the developed algorithm

Explosive processes in the permafrost zone as a new type of geocryological hazard

The natural and human-induced explosive processes in the permafrost area were studied. A new approach is proposed to the theory of formation of gas emission funnels. It is based on the mechanism of migration of gas fluids from the gas hydrates dissociation zone to the overlying permafrost. The dissociation zone is formed in the areas of local heating due to the heat input from above. The preparation stages of the explosive process that formed the Yamal crater are shown. The preparation phases of natural explosive processes have been identified and characterized. Different scenarios are considered for the preparation of natural explosive processes in the cryolithozone. The main conclusions of the conducted research are the following: the explosions of hydrolaccoliths and the formation of gas emission funnels belong to one group of processes, i.e., physical explosions of natural origin; preparation of explosive processes in the permafrost goes through several stages; the migration of gas fluids plays an important role in the preparation of natural explosions in the permafrost. With the ongoing economic development of the Arctic, thermal effects on permafrost increase, and so does the hazard of explosive processes for engineering structures. However, this group of processes is not taken into account when choosing design solutions and predicting the interaction of an engineering structure with permafrost soils; moreover, these processes are even not included in the group of hazardous geological processes.

Using Fast Hot Shock Wave Consolidation Technology to Produce Superconducting MgB2

The original hot shock wave assisted consolidation method combining high temperature was applied with the two-stage explosive process without any further sintering to produce superconducting materials with high density and integrity. The consolidation of MgB2 billets was performed at temperatures above the Mg melting point and up to 1000oC in partially liquid condition of Mg-2B blend powders. The influence of the type of boron (B) isotope in the composition on critical temperature and superconductive properties was evaluated. An example of a hybrid Cu-MgB2–Cu superconducting tube is demonstrated and conclusions are discussed.

FINANCIAL BUBBLE IMPLOSION AND REVERSE REGRESSION

Expansion and collapse are two key features of a financial asset bubble. Bubble expansion may be modeled using a mildly explosive process. Bubble implosion may take several different forms depending on the nature of the collapse and therefore requires some flexibility in modeling. This paper first strengthens the theoretical foundation of the real time bubble monitoring strategy proposed in Phillips, Shi and Yu (2015a,b, PSY) by developing analytics and studying the performance characteristics of the testing algorithm under alternative forms of bubble implosion which capture various return paths to market normalcy. Second, we propose a new reverse sample use of the PSY procedure for detecting crises and estimating the date of market recovery. Consistency of the dating estimators is established and the limit theory addresses new complications arising from the alternative forms of bubble implosion and the endogeneity effects present in the reverse regression. A real-time version of the strategy is provided that is suited for practical implementation. Simulations explore the finite sample performance of the strategy for dating market recovery. The use of the PSY strategy for bubble monitoring and the new procedure for crisis detection are illustrated with an application to the Nasdaq stock market.