Experimental study on the effect of the angle of the shaped charge tube on the penetration enhancement of coal seam blasting

In order to solve the problem of poor permeability enhancement effect caused by disorderly expansion of coal cracks in traditional presplitting blasting, the influence of different opening angles of shaped charge blasting cartridge on permeability enhancement effect of coal seam was studied. By establishing the theoretical model of micro element closure of shaped charge hood, the velocity and mass changes of shaped charge jet were analyzed when the angle of shaped charge hood decreased; On this basis, the mechanism of penetration enhancement by shaped charge blasting is analyzed. A two-way loading gas-solid coupling blasting similar simulation experiment system was built in the laboratory, which can analyze the experimental model from multiple angles of coal macro crack and strain data. The common blasting and different shaped energy opening angle blasting simulation experiments were carried out on the test block of coal containing gas. The results show that the use of shaped charge can effectively guide the directional development of cracks in the opening direction of shaped charge compared with ordinary blasting; With the decrease of the angle of the shaped charge hood, the crack formed after shaped charge blasting is smoother in the direction of energy accumulation, the crack width also increases, and the section of the test block is smoother; According to the inversion results of the super dynamic strain gauge, the peak compressive stress of 60°, 80° and 100° shaped charge blasting at No. 1 measuring point is 1.52 times, 1.26 times and 1.08 times that of ordinary blasting, respectively, and the time to reach the peak stress of 60° shaped charge blasting is the shortest, indicating that with the reduction of the opening of the shaped charge cover, the upward energy concentration phenomenon is more obvious. Four different angles of shaped charge blasting were compared and analyzed by ANSYS/LS-DYNA software. The simulation results show that the effective stress of the shaped charge jet formed initially by 60° shaped charge blasting is the largest, and the crack generated in the direction of shaped charge blasting is the longest. The test and simulation results show that better blasting effect can be obtained by using 60° shaped charge. The research results have certain reference significance for the permeability enhancement of shaped charge blasting in soft and high gas coal seam.