新建上跨既有隧道爆破振速安全阈值研究

Study on safety threshold of blasting velocity of existing tunnel in the new upper span

为研究新建隧道爆破开挖对下方既有隧道衬砌结构的影响特性和控制标准,基于应力波理论分析了应力波在不同介质间传播的透射规律,根据二衬结构的抗拉和抗剪强度,分别推导出既有隧道二衬结构受上方新建隧道爆破开挖影响的振动控制标准。结果表明:爆破应力波对既有隧道二衬结构的破坏效应中P波占主导地位;应力波入射角度与衬砌结构临界安全振动速度呈正相关,临界安全振动速度随入射角的增大而增加;当应力波入射角度相同时,既有隧道二衬结构发生极限抗拉破坏的振动速度小于极限抗剪破坏时的振动速度,二衬结构以抗拉破坏为主;且既有隧道二衬结构发生极限破坏时的最小振动速度出现在拱顶处,最小振动速度安全阈值为15.15 cm/s。

In order to study of the newly built tunnel blasting excavation on the existing tunnel lining structure characteristics and the influence of control standards,based on stress wave theory to analyze the spread between the transmission law of stress wave in different medium,according to the second lining of the structure of the tensile and shear strength,respectively derived both tunnel second lining structure was affected by the above new tunnel blasting excavation of vibration control standards.The results show that P wave plays a dominant role in the damage effect of blasting stress wave on the existing tunnel second lining structure.The incidence angle of stress wave is positively correlated with the critical vibration velocity of lining structure,and the critical vibration velocity increases with the increase of incident angle.When the incident angle of stress wave is the same,the vibration velocity of the existing tunnel second lining structure is less than that of the ultimate tensile failure,and the second lining structure is dominated by tensile failure.The minimum vibration velocity of the existing tunnel second lining structure occurs at the vault,and the safety threshold of the minimum vibration velocity is 15.15 cm/s.