Study On Blasting Vibration Effect Due To Small Clear Interval And Large Cross Section In Shallow Tunnel

People were paid more and more attention to vibration damage of building surface created by blasting excavation in the construction of small interval and large sections in shallow tunnel. How to effectively control the influence of blasting vibration effect created by small interval and large sections in shallow tunnel has become one of the most important research subjects in engineering blasting.The thesis toke Chongqing Shuangbei tunnel for engineering background, combined with the site conditions of tunnel blasting excavation, tested the surface vibration for many times on blasting excavation in the shallow section. Through the analyzing on vibration date when considering the surface elevation changed and not, obtained the attenuation laws and frequency characteristics of vibration velocity in surface. Vibration velocity is the largest in the workface, the vibration velocity with the same distance of ahead workface is greater than the rear. Vibration velocity as the center of workface appears decay laws on both sides of the workface in which the range of20m ahead attenuated fast, and then attenuated gently.Compared with vibration velocity data in surface when considering the surface elevation changed, we founded that:with the height increased where existed elevation amplification effect whose amplification coefficient was between1.06and1.47. The surface velocity of blasting vibration can be described by modified Sadaovsk attenuation formulas. The attenuation factors of vertical vibration velocity attenuation on the shallow ground in Shuangbei tunnel were K=140.55, α=0.728, β=1.297, in which the horizontal were K=101.266, α=0.93, β=1.341.On the shallow section (buried deep25m) to which not considered the surface elevation changed was simulated calculation by numerical simulation software. And then simulated the influence of the blasting vibration velocity of the surface in the four buried deep conditions of25m,20m,15m and10m. Through simulate calculation obtained the vibration velocity influence range of buried depth was between5m rear the workface and20m ahead. With the decrease of the buried depth, vibration velocity was increased gradually. When buried depth is less than the excavation width, buried depth plays an important influence in the increasing of the surface vibration velocity.