Experimental Study on Directional Fracture Blasting of Cutting Seam Cartridge

Since the cutting seam cartridge has sound directional breaking effect, in order to explore its blasting wave mechanism, an experimental study was conducted on the blast wave of a cutting seam cartridge using a high-speed laser schlieren system and air overpressure test system. The research results show that during cartridge explosion, the cutting seam pipe can effectively control the energy release and detonation gas dynamic behaviors. Additionally, the cartridge blast wave and the detonation gas remain highly symmetrical in expansion form. The blast wave first propagates along the cutting seam direction, and the detonation gas initially expands from the seam in the direction of the cutting seam. The pressure in the cutting seam direction is higher than that in the noncutting seam direction. The blast wave change of the whole flow field of the cutting seam cartridge was numerically simulated and was basically consistent with the results of the schlieren test in distribution form. The presence of a cutting seam prolongs the blast wave effect. During expansion of the cutting seam pipe under the influence of a blast wave, the inner wall of the cutting seam pipe is mainly subject to tensile stress. When the tensile force applied to the inner wall reaches the local yield limit, the cutting seam pipe fails.

PATTERN RECOGNITION OF MINE MICROSEISMIC AND BLASTING EVENTS BASED ON WAVE FRACTAL FEATURES

A microseismic (MS) monitoring system in a mine can monitor the MS signals generated by coal rock rupture and blasting waves and can distinguish the two types of waves more clearly to monitor and analyze the rupture and evolution process of coal rock. According to the nonlinearity characteristics of the waveform, the fractal characteristics of a mine’s MS and blasting waves are analyzed by simple fractal and multifractal theory, and the simple fractal dimension [Formula: see text] and multifractal parameters are obtained, respectively. Results show that the simple fractal dimension [Formula: see text] reflects the complexity and frequency structure of the wave. The simple fractal dimension [Formula: see text] of a blasting wave is larger than that of a mine MS wave, which indicates that the blasting wave is relatively complex with higher frequency, while the mine MS wave is relatively simple with lower frequency. However, the simple fractal dimension [Formula: see text] can only describe the wave integrity features, not the local features. The multifractal parameters can describe the local characteristics of the wave more finely, and the multifractal spectrum describes the probability information of the singularity exponent [Formula: see text]. The singularity exponential range and multifractal spectral width [Formula: see text] of the blasting wave are smaller than those of the mine MS wave, which indicates that the probability measure of distribution unevenness and the degree of partial parameter fluctuation of the blasting wave are more severe than those of the mine MS wave. Wave signal analysis based on simple fractal and multifractal methods can not only obtain the characteristics of the wave strength and spectral structure but also other important information, such as local singularity. Therefore, it is possible to more clearly and conspicuously identify mine MS and blasting waves, so that coal rock rupture can be monitored more accurately.

Instantaneous Rock Blasting Wave and Its Microscopic Characteristics during Interaction with Concrete

This paper uses improved technology for dynamic strain measurement to investigate the dynamic strain signals of blasting wave action tested in the range of 8–16 cm from the central blast. Based on the blasting mechanism and on the analysis of signal characteristics, blasting waves are recognized and divided into three zones, namely, shock wave zone, stress wave zone, and gas-expanding zone. This paper studies the relationships between stress, strain, and time of every zone. The tensile and compressive stresses of stress wave are considered. After the blasting test, four cracks from the borehole center toward the minimum burden appear at the model surface. The relationship between blasting wave and concrete damage is analyzed.