Numerical analysis of rock joints in tunnel construction during blasting

In tunnel construction, rock joints cause over-excavation and under-excavation. The finite element method is an effective method for studying the blasting process of jointed rock masses. In this study, a finite element model was established to simulate blasting in a rock mass, and the influence of rock mass joints on over-excavation and under-excavation in tunnel construction was studied. Lagrange and arbitrary Lagrangian–Eulerian (ALE) methods were used. By comparing the two methods, the former method is chosen to calculate the blasting process because the calculation result of the former method is closer to the actual blasting model. On this basis, the blasting process of the intact rock mass and rock mass with vertical, horizontal, and inclined joints was simulated numerically. The results show that the joint has a significant effect on the blasting process. The joint prevents the propagation of the stress wave, and the blasting is limited by the joint; the blasting of a vertically jointed rock mass is limited between two joints; in the blasting of a horizontal jointed rock mass, a plane is formed at the bottom of the hole owing to the action of the horizontal jointed rock mass. Similarly, when the rock mass with inclined joints was blasted because the stress wave propagation was prevented by the inclined joints, an irregular wall was formed near the hole. To avoid over-excavation and under-excavation in the jointed rock mass, it is important to perform numerical simulations of the influence of rock mass joints on the blasting process.