| With the large-scale development of high-speed railway construction,more and more tunnel projects have been built.At present,the excavation of tunnel engineering still mainly adopts the drilling and blasting method.The blasting seismic effect produced by the drilling and blasting method will affect the surrounding environment.Therefore,the tunnel blasting seismic effect and vibration control technology have always been an important research topic in the field of tunnel construction.This paper takes Dizong Tunnel,which is a super-large cross-section shallow tunnel crossing densely populated areas,as the engineering background.After consulting a large number of relevant specifications and literature,the blasting vibration response laws and vibration reduction measures of the mentioned tunnel are studied and analyzed by using the method of theoretical analysis,field tests,signal analysis and numerical simulation.The main work and the research results are as follows:(1)In order to study the propagation law of blasting vibration in strata,a blasting vibration monitoring scheme is designed and monitored on site after consulting the inspection standard of blasting vibration and a large number of literature.The formula of blasting vibration attenuation in the tunnel was established based on the regression analysis by Least Squares Method.The power spectral analysis,wavelet-energy analysis,wavelet packet energy analysis and other signal processing programs are programmed based on MATLAB.Through which the spectral characteristics,time-energy change law,frequency-energy variation law and millisecond blasting actual delay time of the monitoring signal are studied.The main factors of controlling blasting vibration are analyzed,and the propagation law of blasting vibration in the tunnel is formed.(2)Taking a typical multi-storey rubble building in the southwest mountain area around theDizong tunnel as the research object,the response law of multi-storey buildings under blasting load is studied,and the blasting vibration monitoring scheme of multi-storey buildings are designed and monitored on site.The maximum vibration velocity,main vibration frequency,time of duration and change of acceleration with the floor are analyzed.Based on the MATLAB software,the wavelet packet analysis technology was applied to analyze the frequency spectrum characteristics of the vibration signals,the distribution rule of the maximum vibration velocity with the frequency bands,and the energetic distribution pattern with the frequency band,through which the response laws of a multi-layer rubble building under blasting vibration are formed.(3)Based on the knowledge of the attenuation law of the blasting vibration about Dizong tunnel and the response laws of a multi-layer rubble building under blasting vibration,the shock absorption measuresc of the super-large cross-section shallow tunnel was studied.The techniques of multi-level wedge-shaped cut-out for middle and shallow holes,vibration isolation holes,and the blasting hole external delay subarea are proposed.The vibration control standard was determined in conjunction with the specification,and the maximum single explosive volume was calculated using the vibration attenuation formula.The explosion control program was scientifically designed,and the shock absorption model for the super-large cross-section shallow tunnel was proposed.The MIDAS/GTS NX numerical analysis software was used to simulate the shock absorption model.The results showed that the modelcan control the vibration speed below 0.9cm/s.According to the on-site monitoring data and wavelet analysis,the vibration induced by the damping model is analyzed,and the effectiveness of the blasting damping technique and the damping model is validated. |
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