Study on initial stress and damage law of hole wall in water interval blasting

When water seal blasting is used in tunnel excavation, the change of water interval length directly affects the final blasting effect. Therefore, it is important to study the initial stress distribution of blasting stress in the water interval of the blast hole to determine the water interval length. Based on the Starfield superposition method, on the premise of considering the attenuation and superposition of explosion stress wave propagating along the axial direction of blast hole, the calculation formula of initial stress and damage change law on the hole wall of blast hole water interval are obtained, which are simulated and verified by finite element software LS-DYNA. The results show that with the increase of the distance from the explosive, the simulated value and theoretical value of the initial stress on the hole wall of the water interval of the blast hole decay in the form of an exponential function, and the error between the two remains below 10%, and it decreases and increases, respectively, with the increase of the radial uncoupling coefficient and the charge, which is consistent with the viewpoint of the classical blasting theory. It can be seen that the results of theoretical analysis are accurate. Based on the above theory, the total stress of the water interval of the blast hole and the damage radius caused by the water shock wave are calculated, respectively. There is little difference between them, which shows that the hole wall damage of the water interval of water seal blasting is mainly affected by the water shock wave.