上下交叉隧道爆破振动特性研究

上下交叉隧道爆破开挖过程中,确保已开挖隧道在爆破载荷作用下的安全是施工过程中的关键问题.以八达岭长城站隧道工程为背景,对进站层主通道爆破开挖进行爆破振动监测,得到了开挖断面在接近和远离监测点的过程中,各监测点的振速分布规律;对实测波形进行频谱分析,得到了不同频率范围的能量分布及不同时刻的瞬时能量.运用LS-DYNA程序建立上下交叉隧道有限元模型,提取了各监测单元的速度时程曲线及等效应力时程曲线.结果表明:各单元振速分布规律与实测振速分布规律相吻合;各单元的等效应力值小于岩体的拉伸屈服强度,未对隧道岩体造成破坏.结合数值计算结果,依据等效应力判据确定了保证已开挖隧道安全的质点临界振动速度,为上部隧道开挖对下部隧道的爆破扰动控制提供了理论依据.

Study on Blasting Vibration Characteristics of Up and Down Cross Tunnels

During the blasting excavation process of the up and down cross tunnels, it is a key issue to ensure the safety of the excavated tunnel under blasting load. Based on the tunnel engineering of Badaling Great Wall station, the blasting vibration monitoring with the blasting excavation of the main tunnel in the entrance layer was carried out, and the vibration velocity distribution law of each monitoring point was obtained when the excavation section was close to or far from the monitoring point. The frequency spectrum analysis was performed to obtain the energy distribution in different frequency ranges and the instantaneous energy at different times. The LS-DYNA program was used to establish the finite element model of the up and down cross tunnels. The velocity time history curves and effective stress time history curves of each monitoring unit were extracted. The results show that the vibration velocity distribution law of each unit was consistent with the measured vibration velocity distribution law. The effective stress value of each unit was less than the tensile yield strength of the rock mass, and the tunnel rock mass was not damaged. Combined with the numerical calculation results, the critical vibration velocity of particles was determined to ensure the safety of the excavated tunnel according to the effective stress criterion, which provides a theoretical basis for the blasting disturbance control of the lower tunnel by the upper tunnel excavation.