This paper aims at providing a sound theoretical solution to auxiliary central hole and the cutting parameters. For this purpose, the forming mechanism of V-cut cavity for cutting blasting was performed based on the hypothetical rock breaking mechanism of V-cut blasting. A theoretical solution for increasing the critical depth of the auxiliary center cuthole and the criteria for increasing the cuthole diameter of various types of cutholes when the rock attributes, explosive properties, and cuthole dip angle are constant are proposed. (1) If charging length le < 0.75H/sin θ, no auxiliary cuthole is needed. (2) If 0.75H/sin θ < le < 0.75H/sin θ + (2∼4) × 0.1, a central vertical auxiliary hole is needed. (3) If 0.75H/sin θ + (2∼4) × 0.1 < le < 0.75(H/sin θ + Hi/sin θi), a shallow inclined hole is needed. (4) If le > 0.75(H/sin θ + Hi/sin θi), both the central vertical cuthole and the shallow inclined cuthole are needed. Meanwhile, the theoretical solution was verified by numerical modelling with ANSYS/LS-DYNA. Moreover, the field implementation of the V-cut and the auxiliary hole effectively improved the blasting effect in both efficiency and economy.
A highly photosensitive Sb/Er/Ge-codoped silica fiber for fabricating fiber Bragg gratings (FBGs) with strong high-temperature sustainability is presented. The photosensitivity and the high-temperature sustainability of FBGs created in this fiber are examined and compared with those produced in a Sn-doped silica fiber. The results show that the Sb/Er/Ge fiber has a much higher level of photosensitivity than the Sn-doped silica fiber and that the FBGs have a similar high-temperature sustainability of 800 degrees C. The strong fluorescence properties observed from this fiber are also examined.
The fissures are ubiquitous in deep rock masses, and they are prone to instability and failure under dynamic loads. In order to study the propagation attenuation of dynamic stress waves in rock mass with different number of fractures under confining pressure, nonlinear theoretical analysis, indoor model test and numerical simulation are used respectively. The theoretical derivation is based on displacement discontinuity method and nonlinear fissure mechanics model named BB model. Using ABAQUS software to establish a numerical model to verify theoretical accuracy, and indoor model tests were carried out too. The research shows that the stress attenuation coefficient decreases with the increase of the number of fissures. The numerical simulation results and experimental results are basically consistent with the theoretical values, which verifies the rationality of the propagation equation.
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