A Study On Monitoring Technique Of Blasting Vibration Of Large Span Tunnel Underpassing A Highway

With the rapid development of Chinese economy, The scale and the number of high-speed railway increased year by year, so that the phenomenon inevitably occurs that the new tunnel will go under the existing tunnel, or other close-building, so it makes more difficult and affects the safety of the surrounding close-building during the construction process. For blasting of large section tunnels, the initial stress state of the surrounding rock balance is destroyed, rock stress redistribute again, which will impact the adjacent buildings. Therefore, the vibration effect due to tunnel blasting must be studied and monitored. The research work and major achievements in this thesis are as follows:(1)Based on the blasting vibration monitoring experiments of Doupeng mountain which underpasses the Guixin highway, the formation mechanism of the blasting, seismic wave characteristics and classification are described. The relationship of the distance from the point of blasting to tunnel face, with the amount of charge and the speed of vibration are analyzes, the regression analysis of the mornitored data is done by experience formula, and obtained blasting vibration attenuation formulas.(2)Comparing with different blasting vibration waveforms, the maximum vibration velocity caused by the blasting of the cutting hole is obtained. It is directly caused by the charge performance for the vertical speed maximum commonly occurring in the beginning, the direct performance is maximum vertical velocity generally occuring in the initial stage of the waveform, but the maximum level of vibration velocity sometimes occurs in the beginning of the waveform, and sometimes the middle of the waveform, so level of vibration velocity is controlled by the cutting hole and other holes; Blasting most strongly affacts structures with natural frequency OHZ～10HZ and60HZ～100HZ, so such construction would be concentrated on as much as possible to eliminate possible security risks;(3) Based on the blasting vibration monitoring data, the tunnel blasting design is revised to,eet the safety requirements, monitoring the surface settlement of Guixin highway indicates that the highway is safe. It is showed that the tunnel excavation process, blasting construction plan are effective, field monitoring should play a controlling role.The Doupeng tunnel underpassing successfully the existing highway expresses that the blasting vibration monitoring is an effective mean for the safe construction of such projects.