公路隧道爆破对邻近引水隧洞振动响应的分析与实测研究

岳西—武汉高速公路安徽段明堂山隧道下穿横河二级电站的一条引水隧洞,引水隧洞与左线和右线的最小距离为12.4~14.8 m,地质条件为中风化花岗片麻岩Ⅲ级围岩。为保证隧道近距离爆破施工下穿引水隧洞的安全和稳定,采用动力分析软件LS-DYNA建立三维有限元模型,模拟隧道开挖爆破对引水隧洞的振动影响,并在引水隧洞内布置3个爆破监测点,将数值计算结果和现场监测数据进行对比分析。计算结果表明,在均匀介质模型里,质点振动速度与质点到爆源的距离成衰减关系,爆破对引水隧洞的振速影响控制在5 cm/s以内,其中拱脚影响最大,边墙和拱顶次之,拱腰最小。实测结果与计算规律基本一致,爆破后节点振速很快达到最大,并随时间的增加快速衰减,500 ms后振动波基本消散。研究表明实际爆破采用的炸药当量和爆破方式合理,未对引水隧洞结构安全造成明显影响。

Analysis on and Monitoring of Influence of Blasting Vibration of Highway Tunnel on Adjacent Water Conveyance Tunnel

Mingtangshan tunnel on Yuexi Wuhan highway crosses underneath a water conveyance tunnel of Grade II Hydro power Plant on Henghe River. The minimum clearance between the water conveyance tunnel and the left highway tunnel tube and that between the water conveyance tunnel and the right highway tunnel tube are 12.4 m and 14.8 m respectively. The highway tunnel is located in Grade III surrounding rock of moderately weathered granitic gneiss. In the paper, the influence of the blasting vibration of the highway tunnel on the water conveyance tunnel is simulated by means of 3D finite element model established by dynamic analysis software LS DYNA. 3 blasting vibration monitoring points are installed in the water conveyance tunnel, and comparison and contrast is made between the numerical calculation results and the measured data, so as to ensure the safety and stability of the water conveyance tunnel. The calculation results show that in homogeneous media, the vibration velocity of the particle attenuates as the distance from the particle to the explosion point increases; the vibration velocity of the water conveyance tunnel induced by the highway tunnel blasting shall be controlled below 5 cm/s; the influence of the highway tunnel blasting on the water conveyance tunnel at the arch foot is the most serious, followed by that at the side wall and that at the crown, with that at the haunch being the smallest. The measurement result agrees well with the calculation results; the vibration velocity reaches its peak quickly after blasting, attenuates quickly as time goes by, and dissipates after 500 ms. The study demonstrates that the blasting scheme and the explosives quantity adopted for the highway tunnel are rational, which have no obvious effect on the structural safety of the water conveyance tunnel.