Study On Vibration Testing Under Urban Tunnel Blasting Construction And Numerical Simulation On Multiple--Intervals Millisecond Blasting

In recently years, China’s urban rail transit construction is in the ascendant. By now the metro construction of twenty-seven cities is going on or in preparation. The metro line has indeed brought us great convenience. At the mean time it also causes many problems such as vibration and noise.In such case, under the support of the Sino-German international cooperation funds" in complex conditions, studies on the interaction between soil and the structure (Project Numbers:GZ566)", the propagation characteristics and attenuation laws of blasting seismic wave on the ground in studied. Firstly, a multi-channel system including signal acquisition, file management, time-domain analysis, frequency-domain analysis and spectral analysis is developed based on LabVIEW2010; Based on the safety monitoring of Changchun road station-seventy-nine middle school section tunnel excavation blasting in Dalian metro line1project, lots of the monitoring data are obtained through the real-time monitoring during excavation blasting using the vibration acquisition system; Based on the vibration model building of tunnel driving blasting, the surface vibration of Changchun road station-seventy-nine middle school section tunnel resulted from driving blasting was simulated by using universal finite element software ANSYS, and simulation porous more paragraphs blasting with the continuous triangle pulse and reanalysis loading mode. Through comparing the actual measurement data and the simulation results, there got a good result.The collected vibration data is analyzed and combined with the calculation of numerical simulation software. Here are some conclusions:(1) The multi-channel system based on LabVIEW2010consists of signal acquisition, file management, time-domain analysis, frequency-domain analysis and spectral analysis. And the laboratory test and field inspection demonstrate that the system has a high precision for collection and analysis, and strong ability for operation, and it’s suitable for subway tunnel blasting, where the demanding of the instrument accuracy is very high, and the environment around is very complex;(2) The three tests for field vibration show that blasting seismic waves decay along with the increasing of the distance of it from explosive source. The waves decay faster if the distance of it from explosive source, and vice versa;The spectrum curve of the second vibration test shows that the surface vibration energy mainly concentrates around5～12HZ, and the frequency rang above12HZ spreading from the surface tunnel face to the distance is quickly suppressed;(3) Because of the wedge cut blasting in the subway tunneling, shock waves occur in the opposite direction to the tunnel heading or the both sides. By the effecting of those shock waves, maximum of surface vibration acceleration appears in a point before the critical area, not on upper part of the tunnel face, which is mainly effected by the angle, cut quantity, buried depth and other factors. During the excavating tunnel blasting in this test domain, the wedge angle cut method of keeping60degree between borehole of cutting hole eye and working plane, influences the domain in the opposite direction of tunnel heading or the0-40m range on both sides of the cable, which the maximum domain is in28m nearby; The influence of wedge cut blasting on the numerical vibration acceleration of the surface is very small, but that on the horizontal vibration acceleration along the tunnel and the perpendicular of the tunnel is large;(4) The different wave patterns of acceleration curve in numerical simulation decay separately, not superpose, just like those in real test. This phenomenon show the success of the simulation of differential blasting, but the difference in wave patterns between test and simulation is clear in specific waves.(5) Due to the influence of the characteristics of vertical wave, a small fluctuation exists before reaching maximum vibration acceleration in each wave during the acceleration curve in real test, but that doesn’t appear in the acceleration curve of the numerical simulation, in which each band rises to a peak in a very short time;(6) Through the comparison of the numerical simulation results and the measured data, it’s found energy distribution of spectrum curve is wide and shaking frequency is large whether in the horizontal acceleration spectrum curve or the vertical acceleration spectrum curve. In decay laws, the spectrum curve of simulation shows good similarity with that of test. High frequency attenuates obviously along with the increase of the distance from the tunnel face, and frequency spectrum is mainly controlled by low frequency;(7) The wave patterns of vertical acceleration in both left node and right node of tunnel face agree well, but amplitudes are different. The wave patterns and amplitudes of horizontal acceleration in both left node and right node of tunnel face are different:The amplitude of right node decays faster than that of the left node, and the horizontal acceleration of left node grows faster than that of the right node.