1 School of Civil Engineering and Architecture，Changsha University of Science and Technology，Changsha，Hunan 410114，China;
2 China key laboratory of bridge engineering of hunan provincial universities,Changsha university of science and technology,changsha 410114，China;
3 College of Civil Engineering，Hunan City University，Yiyang，Hunan 413000，China
Due to the special structure of transition segment for bifurcation tunnel, the blasting inducing vibration would cause the instability of middle wall and rock mass. Taking the Liuyuetian Bifurcation tunnel transition segment as the engineering background, the blast vibration of early excavated tunnel was being constantly monitored. By analyzing the blast vibration data, the propagation laws of vibration wave of early excavated tunnel under the conditions of different surrounding rock grade and different monitoring position were obtained. The mechanical characteristics of concrete lining of early excavated tunnel were studied under the action of blast vibration of lately excavated tunnel with three-dimensional numerical simulation software. The results show that the maximum radial vibration velocity appears at the near-blast side of middle wall in multi-arch segment. The attenuation range of vibration velocity of interlaid rock wall in neighborhood segment is less than that of middle wall in multi-arch segment. The maximum tensile stress and shear stress on concrete lining of early excavated tunnel caused by the blast vibration occur on the hance and the arch springing of near-blast side, respectively. The relationship between the maximum tensile stress and the maximum vibration velocity of concrete lining for lately excavated tunnel is linear. The critical failure vibration velocity is calculated by fitting formula. The safety control standard of blast vibration in transition section of bifurcation tunnel is established.
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