Principles and experimental verification of similar cut-and-fill blasting technology in coal mine tunnels

Mine tunneling blasting technology is a key technology in mine construction and production, the design and optimization of the tunneling section parameters are of great significance to improve the tunneling efficiency and reduce costs. The design of the hollowing parameters is particularly important, for the actual project, due to the outdated design of the hollowing parameters, resulting in the phenomenon of unsatisfactory blasting effect. Based on the homogenized resistance line theory to optimize the traditional hollowing form, developed a similar hollowing blasting theoretical model, according to the actual engineering cases of hollowing area ratio and eccentricity design model experiments, analyzed the influence of different hollowing hole shape, area and location on the roadway tunneling blasting effect. The results of the study show that: In the past 30 years, in the cases of coal mine rock tunnel blasting and boring projects, most of the roadway section area is concentrated in 10 m2 < S≤20 m2, accounting for 68% of all cases. The arrangement of the hollowing eyes was predominantly square, accounting for 71% of all cases. As the section area increases, the percentage of hollowed-out area in the section decreases from 10.49% to 4.58%. As the height of the section increases, the eccentricity gradually increases in the interval 0≤e < 37.5. In the modeling experiments, the peak stress of the specimen decreased from 145.95 MPa to 94.79 MPa as the cavity area increased. The increase in cavity eccentricity caused the peak stress of the specimen to increase from 105.67 MPa to 130.01 MPa. Combining the results of dissipation energy and fractal dimension, it can be obtained that the larger the percentage of cavity occupation and the smaller the eccentricity the greater the structural strength of the specimen, and the greater the size of the block formed after crushing. The experiment confirms that better blasting effect can be achieved when the proportion of hollowing area B > 10% and eccentricity e≤0.1, which verifies the correctness of similar hollowing theory. The conclusions of the study can be used to solve the current situation of low efficiency of blasting and digging due to irrational design of hollowing trench in actual projects.