Abstract
Shaped energy blasting has been widely used in the field of geotechnical engineering because of its good orientation and high energy utilization. However, the bifurcation of cracks in the direction of energy accumulation seriously affects the precracking effect in the direction of energy accumulation. In order to study the influence of the shaped energy angle on the crack propagation and bifurcation in the direction of energy accumulation, this paper used theoretical analysis and numerical simulation to study the influence of the energy angle on the crack propagation law in the energy-concentration direction. It was found that the energy release rate in the direction of energy accumulation after blasting was the main determinant of crack propagation and bifurcation in the direction of energy accumulation, and it decreased with the increase of the shaped energy angle. When the energy release rate in the direction of energy absorption exceeded a certain critical value, the stress intensity factor K at the crack tip would be affected by the impact load more than the bifurcation toughness KB, resulting in bifurcation of the crack in the direction of the energy. The SPH method was used to simulate and analyze the energy blasting of four different shaped energy angles. The results show that as the shaped energy angle increases when the shaped energy angle is greater than or equal to 35°, the cracks in the direction of energy accumulation after blasting are bifurcated, two cracks at the crack tip. When the shaped energy angle is less than 24°, only one horizontal crack is generated in the direction of shaped energy, which is in good agreement with the theoretical analysis. The research in this paper will provide a certain research basis for the design of the blasting device and the optimization of the blasting effect.
Highlights
With the widespread application of coal-free column cutting and roadway technology and the improvement of underground engineering, blasting excavation requirements, the requirements for the connectivity of cracks, and the linearity of cracks in the direction of shaped energy in shaped energy blasting are increasing. e research and application of shaped energy blasting technology originated from the First World War and began to be mainly used for weapons and equipment
Conclusion is paper used LS-DYNA software to adopt smooth particle flow method to simulate the bidirectional cumulative tensile blasting when the shaped energy angles are 24°, 35°, 45°, and 60°, respectively, to explore the blasting crack growth, bifurcation and equivalent stress development law in the direction of energy accumulation during blasting which were studied in detail, and the effect of energy accumulation devices with different energy angles on the directional blasting effect of rocks
(1) According to the theoretical analysis, during the blasting, the increase of the energy-gathering angle of the energy-gathering device will increase the explosive gas bursting into the fracture to a certain extent, thereby releasing more energy when the fracture expands. e stress intensity factor of the crack tip will increase with the increase of the energy concentration angle, and the increasing trend will become more and more significant
Summary
With the widespread application of coal-free column cutting and roadway technology and the improvement of underground engineering, blasting excavation requirements, the requirements for the connectivity of cracks, and the linearity of cracks in the direction of shaped energy in shaped energy blasting are increasing. e research and application of shaped energy blasting technology originated from the First World War and began to be mainly used for weapons and equipment. The influence of the concentrating holes on the blasting effect is not very clear, which brings some troubles to the further optimization of the concentrating device It causes some problems with the widespread application of bidirectional cumulative tensile blasting technology. In order to study the crack propagation and bifurcation law of shaped energy blasting individually, this paper used LS-DYNA software and applied the smooth particle flow method to simulate the concentrating blasting with the shaped energy angles of 24°, 35°, 45°, and 60°, respectively, and the evolution law of the crack propagation and bifurcation of the energy in the direction of shaped energy at different shaped energy angles was analyzed, providing a certain research basis for the optimization and wide application of bidirectional cumulative tensile blasting technology
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