Numerical simulation of dynamic damage effect of surrounding rocks for tunnels by blasting excavation

It can not only play a guiding role in engineering design in advance predicting the cracking depth and damaged range of surrounding rocks by blasting excavation in use of numerical simulation method, but also is of great significance to construction safety; in which, a scientific and reasonable damage model and iterative calculation method are most important key technique. Based on the user-defined constitutive modules of the fast Lagrangian analysis of continua in three dimensions (FLAC(3D)) procedure, Yang-Liu dynamic damage model dependent on strain rate considering cumulative strain and load time is embedded in Mohr-Coulomb elastoplastic model. The rock damage characteristic is reflected in the iteration calculation process of a incremental load; thus an elastoplastic dynamic damage constitutive model is formed. Subsequently, iterative format of damaged and modified stresses is derived in detail. In simulating a circular tunnel by blasting excavation, a discussion and analysis for characteristics of vibration attenuation and distribution rules of damage in surrounding rock mass induced by blasting are carried out. The calculation result shows that the vibration velocity peak is well correlated with the damage coefficient. The blasting damage model and simulation method can provide a certain reference to similar engineering.