断层带影响下隧道二衬结构爆破振动特性与安全判据

Blasting vibration characteristics and safety criteria of tunnel secondary lining under the influence of fault zone

针对隧道爆破开挖穿越断层破碎带时,围岩松散、破碎,易造成隧道结构失稳的问题。以龙南隧道爆破施工为工程背景,依据现场爆破振动测试结果,建立ANSYS/LS-DYNA动力有限元数值模型,研究了断层带影响下隧道二衬结构爆破振动特性,提出了以应力为控制标准的振速安全判据。结果表明:隧道拱脚处振速衰减最快,破碎带内隧道各部位振速衰减幅度普遍大于相邻围岩段;隧道二衬剪应力峰值位于拱顶处,拉应力峰值位于拱脚处;结合应力与振速关系,建立基于二衬极限强度的爆破振动安全判据,分析得到隧道衬砌在断层带影响下更容易失稳,在龙南隧道爆破条件下衬砌爆破安全振速为10 cm/s,爆破施工单段最大药量为23.89 kg。

Aiming at the problem that the surrounding rock is loose and broken when the tunnel blasting excavation passes through the fault fracture zone,it is easy to cause the instability of the tunnel structure.Taking the blasting excavation of the Longnan tunnel as the engineering background,ANSYS/LS-DYNA dynamic finite element numerical model is established according to the test results of blasting vibration.Then study the blasting vibration characteristics of the secondary lining structure of the tunnel under the influence of the fault zone,and proposes a safety criterion of vibration based on stress.The research results show that the vibration velocity at the arch foot of the tunnel has the fastest attenuation,and the vibration velocity attenuation amplitude of each part of the tunnel in the fracture zone is generally greater than that of the adjacent surrounding rock segment;that the peak shear stress of the second lining of the tunnel is at the arch crown,and the peak tensile stress is at the arch foot;and that through combining the relationship between stress and vibration velocity,and establishing the blasting vibration safety criterion based on the ultimate strength of the second lining.The analysis shows that under the blasting conditions of the Longnan tunnel,the blasting safety vibration velocity at the lining of the broken zone of the tunnel is 10 cm/s,and the maximum dose in a single stage of blasting construction is 23.89 kg.