Effect Of Tunnel Excavation Blasting Vibration On Ground Surface Buildings

With the vigorous development of China’s transport undertakings,:hrough the downtown area of shallow tunnel project will be more and more, due to the:onditions of the project, which requires a large part of the tunnel excavation blasting method, but the effect of blasting vibration generated is likely to endanger the safety of the surrounding buildings. Therefore, to ensure the safety of buildings and the smooth construction of tunnels and underground engineering, it is necessary to study of structural vibration effects under blasting seismic wave.This paper first introduces the blasting seismic wave generation, propagation of its type and theoretically studies the effect of blasting vibration for structural vibration damage mechanisms, namely the direct effects and dynamical response effects. Then under Chongqing XinHongYan tunnel blasting excavation engineering background, blasting vibration characteristics and changes is studied based on monitoring data shallow tunnel surface. Blasting seismic wave frequency, energy distributions are analyzed and the different conditions of blasting seismic wave spectral response characteristics are also analyzed through matlab signal processing functions. Finally, the general structural dynamics theory is referenced and through ANSYS finite element software calculate and analyze dynamical response of engineering example of a frame structure under the action of the blasting vibration, vibration and seismic intensity Dynamical responses under comparison, in accordance with established safety assessment system blasting vibration safety assessment was carried out. Through the above, the paper obtained preliminary conclusions:1) Blasting seismic wave frequency components contained wider band. However, different methods of blasting, blasting vibration signal spectral components have a large difference. The distribution of non-electric detonators fundamental frequency is between40-75HZ. Extension of time using different electronic detonator blasting frequency distribution values are compared with the frequency of large non-electric detonators for blasting. At close range, high frequency seismic waves blasting vibration component content is higher, while in the remote area, the high frequency vibration component content is reduced, the low frequency content of the seismic wave component is increased.2) The main vibration frequency reflects energy distribution.the energy distribution is uniform, the frequency domain in addition to the main vibration frequency outside, there is a plurality of sub-frequency bands, the energy of each frequency band is not the same size, so that a plurality of frequencies resulting in the presence of a peak corresponding to blasting, shows the use of single frequency blasting safety criteria exist biased.Vibration energy distribution of non-electric detonators relatively concentrated in the low frequency range, while the distribution of electronic detonators in high frequency energy than a non-electric detonator with high-frequency band energy is large.3) Shock response spectrum of blasting seismic wave peak interval corresponding period in about0.01-0.05s (corresponding to a frequency of20～100HZ) range, the rapid decay of spectral peaks follows. Acceleration response spectra in a short period (high frequency part) and beating the peaks are more obvious, as the cycle becomes longer, the peaks become smaller and tend to smooth decay.4) Through the structure ANSYS response spectrum analysis and time history analysis, in the role of blasting vibration displacement and internal force distribution and variation of the frame structure is similar to the lower natural earthquake, although blasting vibration acceleration is greater, but the structure of dynamical response values displacements and internal forces such as vibration effect is much smaller than the next earthquake intensity, thus, it can be determined that the structure of the blasting vibration conditions is safe.