大断面隧道爆破开挖围岩损伤范围试验研究及数值计算

NUMERICAL SIMULATION AND EXPERIMENTAL STUDY OF DAMAGE RANGE OF SURROUNDING ROCK IN LARGE TUNNEL UNDER BLASTING EXCAVATION

结合大帽山大断面隧道群的现场声波监测,研究推进式往复爆破作业的双侧壁导坑法施工的大断面隧道的围岩累积损伤范围,声波监测结果表明,在推进式的多次爆炸荷载作用下,围岩将产生一定程度和范围的损伤;侧壁围岩的累计损伤范围主要由与其齐平的导洞I的开挖掌子面爆破决定;其损伤范围随着导洞I开挖掌子面的接近而逐渐增大,当两者齐平时围岩的损失范围达到最大;但当导洞I开挖掌子面逐渐远离和导洞III爆破开挖通过时,围岩的损伤范围并没有扩大,仅导致损伤围岩的损伤程度增大。基于此,在模拟推进式往复爆破荷载作用下围岩的损伤范围时,用与监测断面齐平的单次爆破近似表示推进式的多次爆破,通过DYNA软件将此决定围岩损伤范围的振动速度转化为爆炸压力,再将爆炸压力传递给用UDEC软件实现的各向异性岩体损伤模型,通过与声波监测结果对比,此方法可以较好地模拟推进式往复爆炸荷载作用下围岩的累积损伤范围,并可为类似工作提供参考和借鉴。

Based on the in-situ monitoring of acoustic velocity in Damaoshan Tunnel with large section, accumulative damage range of surrounding rock is studied in tunnel with large section excavating with two side-wall pilot tunnel method of the advancing to-and-fro blasting operations. Monitoring results of acoustic velocity show that surrounding rock will cause damage at a certain degree and range in advancing to-and-fro blasting load operations. The accumulative damage range of surrounding rock is mainly determined by the blasting of excavating face of pilot tunnel I which is parallel to it. The range increases with the approaching of excavating face of pilot tunnel Ⅰ, and reaches the maximum value when the two are flushed. However, when the excavating face of pilot tunnel Ⅰ gradually moves away and the blasting of pilot tunnel Ⅲ starts to get through, it only leads to the increase of damage degree; the damage range of surrounding rock does not expand. Therefore, when simulating the damage range of surrounding rock in advancing to-and-fro blasting load operations, single blasting parallel to monitoring section can be simulated as repeated to-and-fro blasting vibrations approximately. The vibration velocity which determines the damage range of surrounding rock can be transformed into explosion pressure through software DYNA; and then the pressure can be transferred to anisotropic damage model of rock realized by UDEC software. Compared with monitoring results, this method can better simulate the accumulative damage range of surrounding rock in advancing to-and-fro blasting load operations so as to provide for reference in similar engineering projects.