The traditional wedge-shaped blasting scheme is restricted by the limited working space of construction equipment in small to medium-sized section tunnels, which would result in a large angle between the wedge-shaped blasting hole and the tunnel face. A greater confinement of the rock in the blasting area may lead to a short cycle advance, a low utilization rate of drill holes, and high explosive consumption, among other issues. In this paper, the advantages and disadvantages of the wedging shot and the burn cut were compared based on theoretical analysis and formula derivation. And then, the parameters of the burn-cut hole were further calculated. Finally, a short straight hole and wedge-shaped composite blasting scheme was designed, and a field test was conducted in a hard rock circular power tunnel of a hydropower hub project. The results indicate that the high-strain-rate effect should be considered when determining the tensile strength of rock to ensure the rationality of theoretical calculation parameters, particularly in determining the spacing between the charge hole and the empty hole in trench blasting parameters. Compared with the original scheme, the single-cycle blasting footage increases from 1.7~1.8 m to 2.0~2.1 m, the utilization rate of the blast hole increases from 73.91%~78.26% to 86.96%~91.30%, the single-cycle footage and the utilization rate of the blast hole are improved, and the unit consumption of explosives is almost the same as that of the two schemes. Additionally, the unit consumption of the detonator is reduced by approximately 0.4 rounds/m³, and the economic benefits of its application are greater. It has fewer residual eyes on the tunnel face and higher fragmentation by adopting a combination of short burn-cut holes and wedging shots, which is convenient for subsequent slag removal and the next cycle of drilling operations.

In order to investigate the influence mechanism of steel fiber content on the dynamic compression and tensile mechanical properties of concrete, this study conducted dynamic compression and dynamic Brazilian splitting tests on concrete samples with varying impact pressure and steel fiber volume contents(0%C50 element concrete, 2%, 3%, and 4%) using a Hopkinson pressure bar(SHPB) device. Additionally, high-speed photography was employed to reveal the dynamic evolution process of cracks. The test results demonstrate that under the same impact pressure, both the dynamic compressive strength and dynamic splitting tensile strength of steel fiber reinforced concrete samples exhibit a positive correlation with the content of steel fiber. Furthermore, there is also a positive correlation between energy absorption capacity and degree of crushing, indicating that steel fibers effectively inhibit concrete crushing while preventing excessive energy absorption and dissipation in these samples. The upper limit for energy absorption rate in steel fiber reinforced concrete samples ranges from 30% to 36%. Notably, compared to its effect on dynamic compressive strength, steel fibers significantly enhance the dynamic splitting tensile strength of concrete. For applications requiring high-strength or anti-violence characteristics in combination with cost-effectiveness, technical controllability, and test data analysis; incorporating a reasonable range for toughening can be achieved by including 2%~3% steel fiber content into high-strength concrete. Moreover, it is important to note that the action mechanism of steel fibers differs when considering their effects on both dynamic splitting and compression failure in concrete samples. Steel fibers significantly impede crack propagation during dynamic splitting processes; however, separation between the fibers themselves leads to ineffective toughening during dynamic compression."