Blasting‐Induced Vibration Response of the Transition Section in a Branching‐Out Tunnel and Vibration Control Measures

Abstract

Blasting-induced vibration during the excavation of transition section in a branching-out tunnel causes damage and hence affects the safety and stability of the supporting structure and surrounding rock. To examine the effects of excavation and blasting of the transition section in the posterior tunnel on the supporting structures of the anterior tunnel, the influences of the blasting-induced vibration in the posterior tunnel on the anterior tunnel were analyzed under different surrounding rock levels, excavation techniques, distances from explosive source, and net spans. This method was performed by combining numerical simulation with blasting-induced vibration monitoring according to the construction characteristics of the transition section in a branching-out tunnel of a highway. A control technique was investigated to assure the safety and stability of the anterior tunnel during the excavation and blasting of the posterior tunnel. Results demonstrate that (1) the vibration velocity peak behind the blasting excavation surface of the tunnel is higher than that in front. These results suggest paying much attention in monitoring vibration velocity within 10 m behind the excavation surface. (2) The blasting-induced vibration velocity peak on the spandrel at the side that faces the blasting in the anterior tunnel is 2.0–2.5 times than that at the side behind the blasting. Moreover, the blasting-induced vibration velocity peak on the haunch at the side that faces the blasting in the anterior tunnel is 6-7 times than that at the side behind the blasting. (3) Instead of the full-face excavation method, the use of center cross diagram (CRD) technique or side wall pilot tunnel method is suggested for the excavation of surrounding rocks of IV-level, V-level, and III-level with a net span smaller than 3 m. (4) Vibration control measures, such as double wedge-shaped cut blasting and floor blast-hole staged detonation, were adopted by designing and optimizing blasting parameters (e.g., total explosives, maximal segment explosive quantity, detonation order, and detonation interval) in posterior tunnel. According to the test, the blasting-induced vibration velocity peak, which is monitored in the anterior tunnel, can be controlled within 10 cm/s to assure the safety and stability of the supporting structure and surrounding rocks of the tunnel.

Numerical Analysis for Dynamic Response of In Situ Blasting Expansion of Large Cross‐Section Tunnel with Small Net Distance

“…After the completion of the expansion, the tunnel can meet the traffic requirements of a single hole with four lanes, a span of 22 m, and a cross section area of 255 m 2 , of which the span is the largest in China. A rare tunnel group with large cross-section and small net distance is formed by the original tunnel, the newly built tunnel, and the expanded tunnel [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. e cross-section layout of the tunnel group is shown in Figure 1.…”

Simulating the response of buried structures to external blast loads: Methods, challenges, and advances

“…On the other hand, the PPV criterion has also been used in several studies to investigate the failure of tunnels with lining 16,19–22,25,26,84,91,142–144 . The algebraic relationship between effective stress and PPV can also be examined in the case of linings.…”

“…On the other hand, the PPV criterion has also been used in several studies to investigate the failure of tunnels with lining. 16,[19][20][21][22]25,26,84,91,[142][143][144] The algebraic relationship between effective stress and PPV can also be examined in the case of linings. For example, a linear relation in References 2,137 and an exponential relationship in Reference 91 were presented between maximum effective stress and PPV in the lining.…”

“…publications in this field emphasize the safety of urban structures. Among the various applications of this topic are safety assessment of transportation and metro tunnels, 1 civil air defense tunnels, 2 urban utility tunnels, [3][4][5] underground pipelines, [6][7][8][9][10][11][12][13] culverts, 14 as well as safety assessment in excavations near the existing tunnels [15][16][17][18][19][20][21][22] or the extension of tunnels, [23][24][25] and safe storage of explosives. 26 These structures have different cross-sections depending on their function, design, and construction technology 27 as depicted in Figure 1A.…”

Study on Mechanism of Cumulative Directional Blasting of Brittle Karst Limestone in the Guizhou Province

“…Te results show that the peak value of vibration wave in the direction of energy accumulation is signifcant. Wu et al [10,11] studied the response law of blasting stress by the drilling and blasting method and improved blasting parameters and efectively decompressed rock's compressive stresses according to directional rock-breaking technology. Kang et al [12,13] explored the infuence of the material, shape, and angle of the shaped charge cover on the penetration efect.…”