Application of shaped charge hydraulic smooth blasting technology in excavation of arc-shaped tunnel

Arc-shaped tunnels are widely used in engineering sectors such as water conservation, hydropower, highway construction, and mining owing to their advantages in structural stability, load-bearing capacity, and flow dynamics. However, attaining effective blasting outcomes in small-section arc-shaped tunnels under difficult geological conditions using conventional smooth blasting techniques is notably challenging. This study assessed the suitability of shaped charge hydraulic smooth blasting technology for such tunnels. Employing the ANSYS/LS-DYNA software, the rock mass failure mechanisms were investigated under diverse charging scenarios, including conventional cylindrical charge blasting and bottom, middle, and top charges in shaped charge hydraulic blasting. We also compared the hole wall pressure and rock failure modes under water and air interval charging. Field tests in small-section arc-shaped tunnels assessed the blasting effects of shaped charge water pressure blasting versus conventional air interval charging. An empirical formula for the peak pressure and decoupling coefficient under shaped charge blasting was established. Numerical simulations demonstrated that shaped charge blasting not only induces crack propagation in the direction of the shaped charge but also stimulates crack propagation along the axis of the blast hole. Water pressure blasting significantly increases the pressure level and extends the duration of the quasi-static action, thereby facilitating the quasi-static expansion of cracks. Field test results further verify that employing the guiding effect of shaped charge blasting on cracks for arranging blast holes in semi-circular arches and spandrels can reduce over-excavation and under-excavation at the circular arch. To summarize, the research observations indicate that shaped charge hydraulic smooth blasting technology can effectively enhance the excavation quality of tunnels.