Study on attenuation law of blasting vibration in a small clear distance twin highway tunnel

Abstract

In order to study the vibration response characteristics of shared rock in a small clear distance tunnel during blasting excavation, the field blasting vibration monitoring test was carried out based on the Xiaolongmen tunnel of national highway 109. By arranging monitoring points within a certain range of the left arch waist and right arch waist (shared rock) of the posterior excavating tunnel, the time course curve of the blasting vibration velocity is obtained for each monitoring point. Based on this, the vibration characteristics of blasting seismic waves in the left arch waist and right shared rock of the posterior excavating tunnel are analyzed. The results show that the peak value of the blasting vibration velocity of the right shared rock is about 1.23 times larger than that of the left arch waist during the blasting in the posterior excavating tunnel. Through regression analysis of blasting data, it is found that Kright>Kleft, αright>αleft in the Sadovsky formula, which means the shared rock will cause an obvious vibration amplification effect, and the vibration attenuation speed is faster. The vibration energy of shared rock is mainly concentrated at 20~80 Hz. Compared with the left arch waist, the vibration energy distribution range is wider, and the low-frequency vibration energy below 40 Hz accounts for a higher proportion. By further analyzing the blasting vibration characteristics of cut holes and contour holes, the maximum vibration velocity vector sum in the near area of blasting is generated by contour hole blasting, the maximum vibration velocity vector sum in the far area of blasting is generated by cut hole blasting, and the blasting vibration attenuation speed of contour holes is faster.