深埋隧洞钻爆开挖瞬态卸荷诱发围岩振动特性研究

Characteristics of Transient Unloading Inducing Vibration during Blasting Excavation in Deep Tunnels

爆破开挖面上地应力瞬态卸荷产生的围岩振动是深埋洞室爆破开挖动力扰动主要因素之一。针对静水地应力场条件下深埋圆形隧洞浅孔爆破开挖,采用LS-DYNA动力有限元数值模拟方法研究了地应力瞬态卸荷诱发围岩振动的幅值和频率特性及其影响因素。结果表明:在地应力水平一定的情况下,炮孔孔深是影响地应力瞬态卸荷诱发围岩振动的主要因素;随着炮孔孔深的增加,地应力卸荷速率降低,诱发围岩振动的幅值减小、频率降低、质点峰值振动速度随距离衰减变慢。因此可从优化炮孔孔深的角度控制爆破开挖面上地应力瞬态卸荷诱发的围岩振动。

During blasting excavation of deep tunnels, the rock vibration caused by transient unloading of in-situ stress on blast-created excavation boundaries is one of the major dynamic disturbances. For a deep circular tunnel excavation with short-hole blasting method in a hydrostatic in-situ stress field, the transient unloading inducing vibration including peak particle velocity ( PPV) and frequency content was investigated by using LS-DYNA dynamic finite element method. Results show that blasthole depth is the main factor affecting the transient unloading inducing vibration at the same stress levels. With the blasthole depth increase,the PPV and the frequency get decreased due to the reduced unloading rate. The lower vibration frequency at longer blasthole depth leads to slower PPV attenuation as the distance increases. Therefore, the rock vibration caused by transient unloading can be controlled by properly blasthole depth design.