下穿地铁隧道爆破作用下人防隧道的动力效应

Dynamic Effect of Civil Air-defense Tunnel Induced by Blasting of Undercrossing Subway Tunnel

隧道爆破作用下邻近既有隧道的安全性是爆破施工中的重点关注内容,以武汉地铁8号线洪山路站至小洪山站区间隧道爆破开挖为例,研究下穿地铁隧道爆破作用下上方既有人防隧道的动力效应。使用LS-DYNA建立了隧道爆破有限元数值模型,并结合现场振动监测数据验证数值模型的可靠性,对人防隧道的动力响应特征进行研究。现场测试和数值模拟研究表明:随着爆心距的增加人防隧道衬砌结构质点峰值振速(PPV)逐渐减小,PPV最大值出现在爆源正上方;人防隧道衬砌结构稳定性受拉应力控制,隧道底板和拱顶主控拉应力为隧道环向,边墙主控拉应力为垂直方向;衬砌结构最危险截面位于爆源上方,此截面最可能破坏的位置是迎爆侧拱脚,破坏方式为从内至外的拉破坏。基于极限抗拉强度计算分析得到的隧道衬砌结构振速安全阈值为14.9 cm/s。

The safety of adjacent existing tunnels under the effect of tunnel blasting is a key concern in blasting construction.This paper takes the blasting excavation of the tunnel between Hongshan Road Station and Xiaohongshan Station interval of Wuhan Metro Line 8 as an example to study the dynamic effect of the upper existing civil air-defense tunnel under the blasting action of the underlying subway tunnels.A finite-element numerical model of the tunnel blasting was established by LS-DYNA,and the reliability of the numerical model was verified by field vibration monitoring data.Then,the dynamic response characteristics of the civil air-defense tunnel were studied.Field tests and numerical simulation studies reveal that with the increase of the distance to blasting center,the peak particle velocity(PPV)of the civil air-defense tunnel lining decreases gradually with the maximum PPV point located directly above the explosive.The results show that the stability of the civil air-defense tunnel lining is controlled by tensile stress.Specifically,the main tensile stress of the tunnel floor and vault is in circumferential direction,and the main tensile stress of side wall is in vertical direction.The most dangerous section of the lining structure is located above the source of the explosion,and the most likely location of damage to this section is the foot of the arch facing the blast.The damage mode is tensile failure from the inside to the outside.In addition,the safety threshold of vibration velocity of the tunnel lining structure calculated by the ultimate tensile strength criterion is 14.9 cm/s.