A total Lagrange meshless method for modeling the concrete damage evolutions under blast loading

Quantitative evaluations of blasting damage evolutions of concrete structures are the premise of improving the design codes of concrete blasting engineering. However, traditional numerical methods have some limitations in dealing with the large deformation and discontinuity problems during concrete blasting. In view of this, the improved SPH momentum equation considering blasting load is derived. The “birth and death coefficient” χ is defined, and the traditional SPH smoothing kernel function is then improved, thus realizing the simulations of dynamic blasting damage evolutions under the SPH framework. The methods of determining the concrete meso-structures as well as distinguishing different materials are proposed, which can realize the generations of SPH particles such as aggregates, interfacial transition zones and pores. Firstly, four typical numerical examples are simulated: (1) blasting damage evolution model with one blast hole and one 45° prefabricated fissure; (2) blasting damage evolution model with one blast hole and three parallel prefabricated fissures; (3) blasting damage evolution model with one blast hole, one vertical prefabricated fissure and one horizontal prefabricated fissure; and (4) blasting damage evolution model with two blast holes, two empty holes and two prefabricated fissures. The numerical results are compared with previous experimental results to verify the correctness of the improved method. Then, the concrete mesoscopic blasting damage models are established, and the blast damage evolution processes under different concrete mesoscopic structure properties as well as different dynamic blasting parameters are simulated, and results show that: (1) The blasting cracks are limited around the blast hole when the aggregate content is larger, while when the aggregate content is smaller, the blasting cracks expand to the model boundary by propagating around the aggregates. The increase in the pore content leads to a different crack propagation mode: combinations of crack propagating around the aggregates and connecting the pores. (2) The increase of peak stress wave value and blast stress loading rate leads to the increase in the damage degree around the blast hole, but decrease in the damage degree of the whole model. (3) The damage counts increase rapidly in the initial stage of blasting, but maintain a low level in the later stage when the aggregate content is larger, while it is the opposite when the aggregate content is smaller. The increase in the pore content leads to the decrease in the model damage degree. (4) The dynamic blasting parameters donate less effects on concrete damage counts, and the blasting damage counts decrease with the increase in the peak stress wave value and the loading rate.