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Blasting is the primary method for ultra-deep roadway engineering, which is facing the challenge of low footage caused by unsatisfactory blasting effects. Among all the evaluation indicators, the blast-hole utilization rate is the most important index for measuring blasting effect. Consequently, accurately predicting this index is essential for improving roadway excavation efficiency. In recent decades, the field applications of artificial intelligence have emerged as the prime method, yet the issue of data loss and large errors in large-scale data processing remains unresolved. In this study, novel Structured Nonlinear Support Vector Machine (SNSVM) is introduced as the primary research tool. To enhance prediction performance and accuracy, Genetic Algorithm (GA), Particle Swarm Optimization (PSO) and Sparrow Search Algorithm (SSA) are utilized to optimize the hyperparameters of SNSVM. The prediction models comprise fourteen influencing factors, constituting the comprehensive blasting effect prediction system based on artificial intelligence. The principal criteria for assessing the performance of various models are the error correlation coefficients (Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE), R-Square (R2)) and the Receiver Operating Characteristic (ROC) curve (standard deviation rate (γ)). Among the models considered, SSA-SNSVM exhibited the greatest capability when the swarm size is 90. The RMSE, MAPE and R2 values of training datasets are 0.0070, 15.54% and 0.9295, respectively. The RMSE, MAPE and R2 values of testing datasets are 0.0086, 16.37% and 0.9490, respectively. Furthermore, the minimum standard deviation rate of SSA-SNSVM serves as the vital index for measuring the accuracy, with a value of 0.11. Subsequently, the sensitivity analysis results indicate that the most sensitive factor of blast-hole utilization rate is the surrounding rock itself. The comprehensive blasting effect evaluation is of significant importance for the dynamic adjustment of on-site blasting schemes, including roadway excavation, shaft excavation, or pressure-relief engineering. [ABSTRACT FROM AUTHOR]

In order to study the failure pattern of single jointed rock mass caused by the position of the hole of the strip cartridge, dynamic caustic method, fractal theory and high speed photography technology were combined. The derivative crack propagation pattern of defects in adjacent rock strata under blasting and the evolution of the damage of rock strata, where the hole was located, were analyzed. The results show that, with the increase of the distance between the borehole and the joint, the effect of the reflected stress wave near the joint weakened, and the damage on both sides of the borehole and the bottom of the borehole exhibited different variation patterns. The damage on both sides of the borehole decreased gradually, whereas the damage at the bottom of the borehole increased gradually. The defects in the vertical joint direction were present in the adjacent rock strata. The results showed that the influence of the explosion transmission wave on the defects in different positions was different. The defects near the initiation center were destroyed mainly by compression shear, whereas the derivative crack propagation length was small. The defects far from the initiation center were damaged mainly by tensile shear, while the derivative crack propagation length was long. [ABSTRACT FROM AUTHOR]

Drilling and blasting methods have been used as a common driving technique for shallow-hole driving and blasting in rock roadways. With the advent of digital electronic detonators and the need for increased production efficiency, the traditional blasting design is no longer suitable for deep hole blasting. In this paper, a disperse charge cut blasting method was proposed to address the issues of low excavation depth and high block rate in deep hole undercut blasting. First, a blasting model was used to illustrate the mechanism of the deep hole dispersive charge cut blasting process. Then, continuous charge and dispersed charge blasting models were developed using the smooth particle hydrodynamics-finite element method (SPH-FEM). The cutting parameters were determined theoretically, and the cutting efficiency was introduced to evaluate the cutting effect. The blasting effects of the two charging models were analyzed utilizing the evolution law of rock damage, the number of rock particles thrown, and the cutting efficiency. The results show that using a dispersed charge improves the cutting efficiency by about 20% and the rock breakage for the deep hole cut blasting compared to the traditional continuous charge. In addition, important parameters such as cutting hole spacing, cutting hole depth and upper charge proportion also have a significant impact on the cutting effect. Finally, the deep hole dispersed charge cut blasting technology is combined with the digital electronic detonator through the field engineering practice. It provides a reference for the subsequent deep hole cutting blasting and the use of electronic detonators in rock roadways. [ABSTRACT FROM AUTHOR]

• The explosive loading system and caustics system are employed together. • The empty hole can absorb the energy of stress wave and diverge again. • The distance between two holes have an important effect on crack propagation. • The numerical simulation is similar to the image of caustics. In this paper, the crack propagation behavior of a polymethyl methacrylate plate with double holes under explosive load is investigated. The propagation process of the explosion crack is recorded using a new digital laser dynamic caustics system, in which a high-speed camera and the explosion loading are employed. Firstly, the interaction process between the explosion stress wave and the empty hole reflected stress wave is analyzed using caustics. Moreover, the deflection law of the explosion crack is discussed. Secondly, the relationship between the propagation distance, velocity, stress intensity factor of the explosion crack tip, and the distance between the two holes is analyzed. Finally, the explosion process is analyzed using numerical simulations. It is concluded that the evolution law of the explosion stress wave in during the simulation process is similar to the caustics diagram. Lastly, the time-varying law of the stress between the double holes is obtained. [ABSTRACT FROM AUTHOR]