Optimization and Practice for Partition Pressure Relief of Deep Mining Roadway Using Empty-Hole and Deep-Hole Blasting to Weaken Coal

Rockbursts are among the most harmful dynamic disasters, threatening the personnel safety and mine operation. In order to alleviate stress concentration of roadsides and prevent rockbursts, the large-diameter boreholes and deep-hole blasting are employed for partition pressure relief in the deep mining roadway. Combined with failure behavior and stress distribution of the coal, the multilevel division of risk degree for roadsides stress is determined. Based on the orthogonal test of borehole pressure relief in the general danger partition, the response degree of quantitative indexes to main factors influencing the pressure relief effect is considered. The optimal drilling parameters of 120.0 mm diameter, 20.0 m depth, 1.0 m hole spacing, and 5° elevation angle are obtained, determining the stress boundary of safe pressure relief with boreholes. At higher dangerous stress divisions, the optimized blasting parameters through numerical simulation could be obtained as follows: 15.0 m depth, 1.3 decoupling coefficient, and 2.0 m hole spacing, and meanwhile, a stress relief partition of crisscross cracks with 0.61 m height is formed. The roadsides stress could be well controlled within the safe level. Then, an optimal combination of pressure relief is applied to different stress partition of roadsides, and the effectiveness is validated by field test, which proves remarkably applicable for engineering.

Study on Dynamic Evolution Law of Blasting Cracks in Elliptical Bipolar Linear Shaped Charge Blasting

Based on LS-DYNA numerical simulation analysis and comparison with laboratory tests, the blasting crack development dynamic evolution mechanism of elliptical bipolar linear shaped charge is analyzed. The development law of rock crack and optimal radial decoupling coefficient under different blast hole diameters were studied. The results revealed that the blasting with elliptical bipolar linear shaped charge had a remarkable effect on the directional crack formation, and the maximum effective stress of rock close to the position of shaped charge in the direction of concentrating energy is about 2.3 times of that in the direction of nonconcentrated energy. Moreover, the directional crack could be formed by blasting with elliptical bipolar linear shaped charge with different hole diameters, whilst the length of the main crack was related to the radial decoupling coefficient. Particularly, the main crack reached the longest when the radial decoupling coefficient was 3.36.

Wideband microstrip dual polarization radiator for X-band APAA

In this paper the model and the construction of a wideband microstrip X-band radiator of active phased antenna arrays have been presented. The basic demands to the radiator have been formulated. The results of computer electromagnetic simulation of the radiator in free space and in the infinite array have been given, as well as the results of radiator experimental testing in the waveguide simulator. The characteristics of a proposed radiator such as VSWR, decoupling coefficient and losses have been simulated and estimated experimentally on the test sample. Experiment has shown good agreement with numerical simulation results. Particularly, 20% bandwidth with VSWR no greater than 2 has been achieved. Sample testing in a waveguide simulator gives 0,5 dB loss (active and return loss in radiator without loss in simulator itself). Scan angle at 3 dB gain loss, as it follows from numerical simulation results, should be no less than ±40° or ±45° in the main planes. So, proposed microstrip radiator may be used for X-band active phased arrays, which should work in 20% bandwidth with steerable polarization.

Assessing the decoupling of economic growth from environmental impacts in industrial regions of the Russian Federation: an impact decoupling approach

The article analyzes the dynamics of the economic activity level in Russian industrial regions and its impact on the main environmental elements (water, air and soil) by calculating the decoupling coefficient. In the study a hierarchical cluster analysis was carried out, resulted in the formation of seven regional clusters, five of which had a significant share of the industrial sector in the gross value-added structure. Decoupling coefficients were calculated for 64 constituent entities of the Russian Federation belonging to different types of industrial clusters. The ecological and economic balance assessment of industrial regions growth showed the decoupling effect presence for most of them. The movement towards environmentally sustainable growth is more evident in the regions of the industrially diversified cluster. The analysis of three decoupling coefficients showed that in the vast majority of industrial regions the growth rates of pollutant emissions into the atmosphere and the growth rates of polluted wastewater discharges into surface water change at a lower rate than per capita GRP, which indicates a “green trend” in the region’s economic activity. However, the decoupling coefficient, showing the dynamics ratio of production and consumption waste and GRP per capita, has negative value in 37.5% of regions. The most problematic one in terms of this indicator was the Trade and manufacturing cluster, including 21 constituent entities of the Russian Federation. According to the authors, it may be related to the trade sector of these regions.

Resource efficiency and environmental impact assessment in the region by decoupling method

The conceptual model of decoupling points to an ideal goal when economic growth and human well-being will increase simultaneously with a slowdown in the rate of resource use and environmental degradation. In foreign practice, the de-coupling methodology is used to measure progress towards sustainable development. The relevance of the decoupling method lies in the possibility of its use as a tool for assessing the environmental situation in relation to economic devel-opment. The purpose of the study is to identify the effect of decoupling in the ecological and economic activity of the Komi Republic. Тhe algorithm of decoupling analysis includes the definition of specific indicators of resource efficiency and the load of the polluting impact on the environment, the determination of indicators of resource decoupling and impact decoupling, the rate of change in the economic and environmental indicators, visualization of the calculated indicators. It is established that in the period 2007-2020, the change in the pace of economic development determined the existence of various types of interrelation between economic indicators, resource and environmental performance, estimated by the value of the decoupling coefficient. This is manifested in the fact that under conditions of synchronously decreasing trends in GRP and water resources use, there is no decoupling effect, while at the same time, reducing the negative load on the atmosphere at a higher rate than reducing GRP ensures the existence of relative decoupling. An analysis of the dynamics of indicators reflecting the effectiveness of measures taken to reduce resource intensity and improve environmental efficiency showed that the planned levels of regional indicators by 2020 have not been achieved in most of the target criteria. The factors that determine the unfavorable environmental situation in the region are identified. The main measures that reduce resource intensity and provide a favorable environment are considered.

Influence of Decoupled Charge Structure and Filler on the Blasting Effect

This study compared models of specimens with different filler media and decoupled charge structures in terms of the blasting effect. The test system combined a high-speed camera and high-speed static strain test analyzer. A physical model of a concrete single-borehole decoupled charge structure was designed to study the geometric elements of the blasting funnel, flyrock launch velocity, peak strain values, and distribution of the gravel lumpiness. The experimental results showed that for the same decoupling coefficient, when expandable polystyrene foam (EPS) was used as the filling medium, the radius, depth, and volume of the blasting funnel of the model specimen were larger, the flyrock launch velocity was slower, the peak stress of the specimen was higher, and the distribution of gravel lumpiness was more even. The relationship between the experimental index and the decoupling coefficient follows the changing trend of first increasing and then decreasing or first decreasing and then increasing. With air and EPS as the filling media, the concrete model specimens could achieve optimal blasting effects at decoupling coefficients of 1.83 and 1.69, respectively. The results confirm the feasibility and practicability of using EPS as a filler and can provide guidance and an experimental basis for the selection of the decoupling coefficient and filling medium in blasting engineering.

Theoretical Study on Radial Distribution Laws of Rock Mass Damage Factors under Decoupled Charge Blasting

In this paper, the radial distribution laws of damage factors under decoupled charge blasting are studied for the optimization design of blasting parameters. Through defining the critical radial decoupling coefficient, the damage zone around the borehole is partitioned and the characteristics are described. Based on the damage factor defined by Taylor’s effective elastic modulus, the formulas of the radial distribution laws of damage factors are derived by the attenuation law of stress wave and the theory of thick-walled cylinder, respectively, which are then superposed to obtain the formula under the combined action of explosion stress wave and quasistatic gas. Experimental verification indicates that the theoretical values, which have a good correlation with the test data and are of high accuracy, can characterize the radial distribution laws of damage factors and estimate the damage range. When a radial decoupling coefficient is less than the critical value, the attenuation rate of damage factors firstly increases and then decreases with the increase of distance, and a serious damage zone is caused. Conversely, it decreases gradually, and the serious damage zone is not caused. Therefore, on the premise of stable detonation, it is necessary to apply an appropriate radial decoupling coefficient which is larger than the critical value to smooth or presplit blasting.

Influence of Seismic Source Parameters on the Excitation Wavelet in Seismic Explorations Based on Numerical Simulation

Explosives are the most common seismic source in seismic explorations, whose excitation effect is closely associated with their properties, weight, buried depth, and charging constitution. This study analyzes the influence of seismic source parameters on the features of the explosion wavelet. The explosion process of the seismic source in marine carbonate is numerically simulated with the finite element software LS-DYNA. We consider three parameters, including buried depth, charge weight, and decoupling coefficient. To verify the simulation outcomes, we also carry out field observations. The appropriate buried depth of the explosive should be determined according to stratum lithology. As the charge weight increases, low-frequency energy of the source wavelet increases rapidly. The optimum charge weight is 16–18 kg, and the ideal charging structure is in a concentrated, short-column shape. Compared with the buried depth and charge weight, the decoupling coefficient shows more noticeable influence on the excitation effect of the source wavelet, and the optimum coefficient lies between 2.5 and 3. The results of this study may provide reference data for designing explosion parameters in field seismic explorations.

Study on the Decoupled Charge Effect in Deep-Hole Cumulative Blasting of Coal Seam

Five models of cumulative blasting are established by using ANSYS/LS-DYNA to study the effect of decoupling coefficient on cumulative blasting to improve coal seam permeability. The formation and migration process of the shaped energy jets with two kinds of decoupling coefficient are compared and analyzed; also, the propagation of explosive stress waves is represented. The result showed that the air in the blast hole is the key to the formation and migration of the condensing jet. The air in the hole also could reduce the attenuation of stress wave in a certain range. However, if the decoupling coefficient is too large, the air in the hole will consume excessive explosive energy, which is also not conducive to energy transfer. Therefore, there is an optimum decoupling coefficient which can minimize the coal crushing area, increase the coal fissure area, and improve the gas extraction rate. Besides, the cumulative blasting tests were carried out in a coal seam. The test results show that decoupling charge could effectively improve coal seam permeability, and the blasting effect was better when the decoupling coefficient is between 1.67 and 2.