横通道爆破施工条件下水平耦联隧道动力响应研究

Dynamic responses of a coupled tunnel system with transverse passage under construction blasting load

为研究横通道施工爆破荷载作用下大跨小净距耦联隧道的动力响应规律,依托广州市黄埔区一新建隧道与既有隧道间车行横通道的爆破掘进施工,建立了等效爆破荷载作用下既有隧道动力响应分析的三维有限元计算模型,分析了既有隧道的动力响应规律并进一步确定了当前施工参数下横通道爆破作业面距既有隧道的安全距离阈值。研究结果表明:既有隧道迎爆侧下拱腰区域为主要的振动响应区,衬砌最大振速与最大拉应力均位于该区域内,且衬砌振速主要以水平径向(沿横通道轴线方向)振速为主,施工时可以该位置的水平振速监测值作为横通道爆破施工影响的评价指标;横通道爆破荷载下既有隧道衬砌动应力分布规律及其发展趋势与振速基本一致,且两者具有良好的线性正相关性;既有隧道衬砌峰值振速与开挖面距该隧道距离呈良好的负幂指数关系,基于其拟合关系,建议在横通道掌子面距既有隧道衬砌10 m左右时就应对爆破施工参数进行优化与降级,避免影响既有衬砌的结构安全。

In order to investigate the dynamic responses of a coupled tunnel system with large span and small clear distance under the blasting load generated by the construction,a 3D finite element numerical model for dynamic responses analysis of excavating a transverse passage from a constructing tunnel to an existing tunnel under the equivalent blasting load is established.The law for the dynamic responses of the existing tunnel is analyzed,and the threshold value of the safe distance between blasting surface of the transverse passage and the existing tunnel is determined under the current construction parameters.The results show that the main affected area of the lining lies at the lower arch waist that faces the blasting directly,where both the maximum vibration velocity and the maximum tensile stress appear.The horizontally radial vibration velocity(along the axis of the transverse passage)makes the main contribution to the overall vibration velocity of the lining.Therefore,the monitoring data of the horizontal vibration velocity at this position can be treated as the evaluation indicator for assessing the influences induced by the blasting construction of the transverse passage.The distributed law and varying trend of the dynamic stress of the existed tunnel lining are similar to the vibration velocity,showing a satisfied positive linear correlation between them.There is a negative power exponential relationship between the peak vibration velocity of the existing tunnel lining and the distance from the excavation face of the transverse passage.In order to avoid the unfavorable influences on the safety of the lining structure,the current parameters of the blasting construction are suggested to be optimized when the distance between the excavation face of the transverse passage to the existing tunnel reaches 10 m.