Dynamic Response Of Adjacent Tunnel Subjected To Explosive Loading

During the process of neighborhood tunnel excavation by blasting method, it had great influence on the safety and stability of the former tunnel when the later tunnel was excavated. Dynamic response of former excavated tunnel due to explosive loading was studied through certain technology and research methods, which indicated not only significant theoretical meaning and practical value, but prominent economic benefits and social efficiency.According to the practical project of Baogaishan tunnel, finite element method was introduced to analyze the dynamic response characters of adjacent former tunnel subjected to explosive loading caused by the later tunnel excavation. Tests on tunnel blasting vibration effect were conducted, and then quasi-two-dimensional single-layer mesh models and three dimensional models were established for thorough research. The dynamic behavior regularities of vibration velocity, stress and displacement of surrounding rock and lining were discussed under various working conditions. The main content and work contained in the paper were as follows:(1)With the analysis of blasting vibration monitoring and testing results, propagation attenuation law of seismic wave in the mid of rock was obtained, and thus the maximum explosive charge under safe condition was calculated.(2)On the basis of summarizing former all kinds of explosive loading models, combined with considering relative empirical formulations and practical blasting parameters, simplified millisecond blasting loads model was established.(3)The single-layer model of tunnels was established by utilizing MIDAS/GTS software. The distribution changing laws of dynamic characters (including vibration velocity, stress and displacement) of former tunnel surrounding rock and lining were studied systematically under various tunnel spacing conditions.(4)Through the dynamic analysis of three dimensional tunnel models, the vibration behavior distribution law along the portrait direction was studied and several conclusions were drawn in the end.