Modelling the blast cracking processes of rock masses using a total lagrange meshless method

The dynamic damage of surrounding rock masses has a great impact on the tunnel stability during the drilling and blasting construction processes. However, traditional FEM has some difficulties in simulating the blast damage processes of rock masses during mesh re-divisions. In our work, the smoothing kernel function in traditional SPH method has been improved, and the momentum equation considering the blasting load is derived, which realizes the modeling of the dynamic damage evolution processes under the SPH framework. Firstly, two typical examples are numerically simulated: 1) Upper slow and lower steep “Y” shaped fissure and 2) Upper short and lower long “Y” shaped fissure. The simulation results are compared with previous experimental results to verify the correctness of the SPH method. Then, the progressive blast damage processes are simulated, and the effects of different stress wave loading modes, different pre-existing fissure distances, different fissure dip angles as well as different ground stress levels on the blast cracking morphologies are investigated. Results show that: The blast cracks first appear around the blast hole, then the radial cracks propagate to the model boundary; The radial crack length increases with the increase of peak blast stress wave; The length of the horizontal radial crack decreases and the length of the vertical radial crack increases with the increase of the horizontal ground stress; The existence of pre-existing fissure prevents the further extension of the blasting cracks, and the increase of the fissure dip angle leads to the crack propagation at the fissure tips; The increase of fissure distance leads to the larger crack propagation in the around the fissure; The damage count increases with the increase of peak blast stress wave; The increase of the ratio of horizontal stress to vertical stress decreases the damage count; The damage counts increase with the increase of fissure dip angles; The damage degree of the model increases with the increase of the fissure distance. • Traditional SPH method was improved to simulate the brittle fracture processes. • Blast damage simulations are realized in SPH. • Influencing factors of deep rock blast damage are discussed.