Verification of Theoretical Model and Vibration Effect Caused by Blasting in Shallow Buried Tunnel on Mountain Slope

Results on the blasting vibration effect and influence range of a mountain tunnel under a slope terrain and shallow buried soil in rock composite stratum conditions are presented. The objective was to verify and obtain an accurate and applicable theoretical model of vibration velocity based on a case study by taking the De-ge tunnel in the project of No.317 national highway that passes below a densely populated county. The 4 usual theoretical models were verified by on-site blasting vibration monitoring and regression analysis. Simultaneously, the vibration velocity, the influence range of vibration and the blasting vibration effect were analyzed through 3-D numerical simulation and comparison with theoretical calculations and field measurement results. The results show that: the degree of fitting of the 4 usual theoretical models is 0.15−0.86, and the theoretical model formulas by Tang, Zhu, and Zhou can complement each other with respective advantages in terms of different blasting horizontal distance and elevation difference. The influence range of blasting vibration obtained by the theoretical model is closer to field measurements than the numerical results. The " hole effect” located on the surface within 28 m of the completed tunnel is clear and the maximum vertical vibration velocity increased from 1.98 cm/s at the initiation point up to 2.23 cm/s at the surface. The " slope effect” is remarkable in 10−20 m from the middle line on the downslope surface. The vertical velocity decreases linearly with the increase of the detonation distance when it reaches 1.83 cm/s. The " elevation amplification effect” on the adverse slope will occur within 5−10 m on the other side of the center line as the elevation increases. In the above range on the ground surface, the protected buildings should be the key points of field monitoring, and the earthquake precautions should be strengthened.