Research Of The Numerical Simulation For City Tunnel Excavation Blasting Seismic And The Control Of Blasting Vibration Effects

With the development of China's traffic, a great deal of shallow tunnel in downtown area will be constructed, in which some tunnels need to be excavated by blasting because of engineering and environment conditions. The vibration effects produced by blasting will endanger the safety of buildings close to tunnel. As a result, it is an urgent problem that how to forecast the vibration effects and control it so as to ensure the safety of building in engineering.In this paper, based on the safety monitoring of JIA HUA tunnel excavation blasting in the Jia Hua bridge project, combined with volume test data, the subject investigated is vibration field, which is caused by tunnel excavation blasting. The main work is:①This thesis, by elaborating the theories of rock blasting fragmentation mechanism and theoretical model, points out the influencing factors of rock blasting and explains the types and features of blasting earthquake wave, and analysis evaluation standard of rock blasting both at home and abroad.②The influence that the blast vibration by the tunnel digging acted on the ground buildings were monitored, and lots of the monitoring data were obtained. The monitoring data collected from the scene of blast were analyzed, and the safety evaluation to the influence that the blast vibration acted on the ground buildings was carried. Through regression analysis on the field data by the least square method, the parameter value k,αin the empirical formula which is fit for the area are decided. In this paper, FFT is used to analyze the field data to get tunnel excavation blasting seismic wave's frequency.③Taking the design and measured data of foundation excavation project of Jia Hua tunnel as the sample and the grey correlation analysis methods, the author works out the primary and secondary order of factors influencing blasting vibration effects.④Tunnel blasting is simulated through LS-DYNA/LS-DYNA dynamical finite element program to get seismic wave's transmission law. At the same time, the velocity field and stress field are obtained. At the end, based on the simulative data, the FFT method is used to analyze seismic wave and its frequency character is got. Contrasting with field data, the established simulation method can predict and ansalysis the vibration of engineering blasting. ⑤Based on the theory of control blasting, combining the results of gray analysis and numerical simulation, the author brings forth several measures for vibration absorption. So as to control the vibration velocity of ground within safety range in the process of this tunnel excavation construction, consequently the safety of ground buildings of construction segment and blasting work of this tunnel project was insured.