Dynamic Mechanical Characteristics of Horseshoe Tunnel Subjected to Blasting and Confining Pressure

The blast loading direction and in-situ stress field have an effect on the destruction process in the surrounding rock around the tunnel. Five blasting directions are considered in the experiment and simulation. The static stress distribution by confining pressure and the superposition stress waves process are discussed by simulation in LS-DYNA. Results indicated that the hoop stress accelerates the radial cracks growing, and the damage around the hole is not influenced by the blasting direction. The stress wave superposition and failure process along the tunnel are affected by the blasting direction. The distribution of static prestress is symmetrical under the uniform confining pressure (k = 1) and decelerates the crack extension by confining pressure. Under the non-uniform confining pressure loading (k ≠ 1), the tensile prestress is formed with a k increase and accelerates the horizontal crack propagation after blast loading. The concentrated stress is serious in the partial region along the tunnel, especially in the vault position under the static-dynamic coupling loading. Notably, the horizontal destruction area between the hole and the tunnel further expands when k increases.