Vibration Propagation Law in Different Areas of Tunnel Face Caused by Blasting

According to the position and role of borehole, the tunnel face is divided into three regions undercutting area, auxiliary area and surrounding areas and each region have different blasting vibration attenuation law. Using blasting vibration testing instrument TC-4850, the vibration caused by blasting excavation in different region of Chongqing terminal connecting line tunnel was monitored and analyzed, and the vibration characteristics and attenuation law of different region in tunnel face were gained. The results show that: the maximum blasting vibration value was produced in cutting area of tunnel; using the partial excavation and setting large diameter hollow hole in the cut area can effectively reduce the blasting vibration, and the more the number of hollow hole, the damping effect was more significant; vibration attenuation parameters were different in different blasting area in tunnel face and with the increase of excavation area, the vibration attenuation coefficient was gradually decreased. Vibration attenuation index was determined by the geological conditions, basically unchanged, the value of the auxiliary area was 0.5~0.67 times the cutting zone, the value of the surrounding area was 0.25~0.33 times the cutting zone. When adopting sub-steps and sub-regional excavation in small spacing tunnel of Chongqing area, vibration attenuation coefficient can be valued by cutting areas 110~120, auxiliary area 60~80, surrounding region 30~40 and vibration attenuation index can be valued by cutting area 1.5, auxiliary and surrounding region 1.6.