YANG Hangpeng1, YU Jin1, FU Xiaoqiang1,2, YAO Wei1, LIN Congbo1, CHANG Fangqiang1
JOURNAL OF VIBRATION AND SHOCK. 2023, 42(1): 46-53.
Clarifying the law of rock damage in the bifurcation small net distance tunnel under the condition of alternating blasting construction will help to better ensure the construction of the tunnel site and the stability of the surrounding rock. The three-dimensional finite difference software FLAC3D simulated the excavation process of the bifurcated small net distance tunnel under the action of blasting load, focused on the damage distribution and evolution of the middle rock under different excavation conditions, and finally verified by the on-site acoustic damage range detection results of the Xiamen Haicang Dredging Channel Bifurcation Tunnel Project. The results show that the stress wave generated by blasting reflects at the fork to form tensile stress, which makes the damage to the fork section more serious; the damage to the sandwich rock in the tunnel is asymmetrically distributed, and the damage from the inside of the middle sandwich rock to the contour line gradually increases, the maximum damage of the middle rock on the main tunnel side is in the range of 90 ° to 120 °, the maximum damage of the middle sandwich rock on the ramp side is within the range of 90 °, and the thickness of the middle sandwich rock has a greater influence on the damage of the middle sandwich rock, and with the increase of the thickness, the degree of damage of the middle between the rock decreases and the damage range does not penetrate the left and right tunnels; Through the simulation to change different approaches, excavation staggered distance and excavation sequence, it is found that compared with 2m, the complete damage area of 5m approach is increased by 58.5%, the damage penetration area is increased by 70%, the complete damage area of the staggered 1 step is increased by 1.27m compared with the staggered 4-step working condition, and the damage penetration range is also increased, and the excavation of a smaller section is conducive to the stability of the middle rock, and the symmetry of the surrounding rock damage is better, but the damage to the rock mass on the side of the middle sandwich rock will be expanded, and the numerical simulation results are basically consistent with the actual measurement results of the site. The simulation results provide certain references for the construction of the small net distance tunnel of the bifurcation of the highway.