硬质地层下近接隧道爆破振动影响分区及动力响应研究

Impact Zoning and Dynamic Response to Blasting Vibration in Adjacent Tunnel under Hard Rock Strata

为探究硬质岩地层下立体交叉隧道近接爆破施工对既有隧道的影响程度,依托福厦客专新大帽山1号隧道和既有新刘塘1号隧道,以基于国内爆破振动规范的“频率-振速”双判据作为分区标准,对新建隧道爆破振动影响分区及动力响应展开研究。首先,通过三轴试验和Hoek-Brown准则得到计算参数;其次,对不同工况下新建隧道爆破振动规律开展研究,得到爆破振动影响分区;最后建立三维有限元模型,探究新建隧道在既有隧道正下方爆破时既有隧道的动力响应规律。研究结果表明:(1)通过迎爆侧最大振速衰减曲线,分析得到依托工程的爆破振动影响分区,判断既有隧道处于弱影响区;(2)爆破对上下方向的影响范围大于左右方向,得到硬质岩地层单线铁路隧道的爆破振动影响总分区;(3)爆破对未开挖段上方既有隧道的影响范围大于已开挖段的影响范围,且由于介质反射,导致已开挖段上方既有隧道振速衰减较慢;(4)通过现场监测结果验证了数值模拟的正确性,且既有隧道结构变形及受力均满足影响控制要求。

To investigate how the blasting of overlapped tunnels affects adjacent existing tunnels in hard rock strata,a study is carried out on the impact zoning of the blasting vibration and dynamic response of new tunnels based on the"frequency-velocity"criterion specified in China′s standards for blasting vibrations,with the new Damaoshan No.1 Tunnel and the existing Xinliutang No.1 Tunnel on Fuzhou-Xiamen Passenger Dedicated Line as the study case.First,the calculation parameters are obtained through triaxial tests and the Hoek-Brown criterion.Second,the blasting vibration pattern of new tunnels under different cases is studied and the impact zoning of the blasting vibra⁃tion is obtained.Finally,a 3D finite element model is established to investigate the dynamic response pattern of the existing tunnel when the new tunnel is being blasted directly below the existing tunnel.The results show that:(1)the impact of the project′s blast vibration can be zoned through the maximum vibration attenuation curve on the blast face and it can be determined that the existing tunnel is in the weak impact zone;(2)The impact range of blasting in the up and down directions is greater than that in the left and right directions,and the total impact zones of blasting vibration can be obtained for single-track railway tunnels under hard rock strata;(3)The impact range of blasting on the existing tunnel above the unexcavated section is greater than that on the excavated section,and because of me⁃dia reflection,the attenuation of the vibration speed of the existing tunnel above the excavated section is slow;(4)the correctness of the numerical simulation is verified with the field monitoring results,and it is found that the defor⁃mation and stress of the existing tunnel structure both meet the requirements for impact control.