Study On Ground And Original Near Tunnel Vibration Under New Urban Shallow-buried Tunnel Blasting Construction

With the rapid development of economic construction, there have been an increasing number of road tunnels in our country. During the highway tunnel construction, it often happens that a new tunnel will be constructed behind an original one. Thus, blasting of the new tunnel construction will cause the earth surface above the new tunnel vibration,which is bad for the building safty.It also will make the original tunnels nearby vibrate ,which will affect the stability of the tunnels.Based on Dadukou Shuangshan Tunnel,by virtue of analyzing the resulta of tunnel field monitoring measurement,the study about the blasting construction procss has been executed by the way of numerical simulation.At last, the circular tunnels with different surrounding rocks and spacings ,and the ones with different depths are studied in order to disclose the mechanical effects of the original tunnles during the vibration.Here are some conclusions:①The attenuation of the blasting seismic wave increases with the distance, which the velocity of attenuation has something to do with .The attenuation is quite obvious when it is near the explosion source, nevertheless this is not correct when it is far from the explosion source.According to the surface particle velocity attenuation formula calculated through statistics principle, the largest quantity of charges in one time is obtained,which could be taken as a reference for the construction of similarity in future.②The blasting numerical simulation results of Shuangshan Tunnel show that the most dangerous part of the original tunnel is the near side wall ,where the level velocity of vibration, maximum stress values are significantly higher than those in other parts. It is a major part to bear blasting load.③The blasting numerical simulation results show the relationship bettween tunnel spacings and vibration of original tunnel. The maximum horizontal velocity of sidewall quickly attenuate from 0.5D to 1.5D,and the changes are not obvious during the spacing more than 2.0D.Both x and y directions displacements of the original tunnel lining are obvious with the spacings less than 1.5D.④The blasting numerical simulation results show the relationship bettween surrounding rocks and vibration of original tunnel. Under the different surrounding rocks ,its maximum horizontal velocity were greater than the vertical velocity,so the horizontal velocity is in the lead.With the same spacing, the better the surrounding rocks is,the greater the greatest vibration velocity of lining is.When the tunnel spacing is less than 1.0D, the first principal stress of tunnel side wall with II,III and IV surrounding rocks is obviously impacted that the tensile stress is in place of compressive stress because of the gravity field, the first principal stress of tunnel side wall is over the tensile strength of concrete with the spacing of 0.5D and II surrounding rocks.With the same tunnel spacing, the worst the surrounding rock is, the larger the displacement of the tunnel lining is.⑤The blasting numerical simulation results show the relationship bettween tunnel spacings and vibration of original tunnel. The greatest velocity of tunnel is less affected by blasting with the depths more than 2.0D. Changes of the depths have more significant impact on the first principal stress of tunnel side wall than it of other parts. Both x and y directions displacements of the original tunnel lining decrease with the increasing depths.The changes of displacement are significant during the depth less than 2.0D.