露天边坡爆破施工对下穿隧道扩大段的影响

针对露天边坡与既有下穿隧道的协同爆破施工,为确保上部边坡爆破开挖作用下既有隧道围岩稳定与安全,以某石油储备基地扩建项目为工程背景,利用ANSYS 18. 0建立上部露天边坡与既有下穿隧道协同施工的数值计算模型,研究露天边坡爆破施工对既有下穿隧道扩大段的影响。结果表明:上部边坡爆破施工激发向下传播的初始纵波,随着距离的增加逐渐衰减,到达隧道拱顶自由面折反射形成面波而后在拱与边墙交点处产生叠加现象,导致面波向下传播的规律为先增大后减小。相比于隧道扩挖前,扩挖后隧道断面拱顶质点Z向振动速度峰值提高68. 1%,为7. 58cm/s;拱顶单元动态拉应力峰值提高150%,为0. 45 MPa。根据《爆破安全规程》要求,隧道围岩在上部边坡开挖爆破荷载作用下是稳定的。建议在实际施工中,将隧道扩大段的开挖时序安排在上部边坡爆破施工区域远离隧道扩挖段之后。研究成果对地下近接隧洞爆破施工及隧道扩挖工程具有重要参考价值。

Impact from blasting construction of open-air slope on expanding section ofexisting undercrossing tunnel

Focusing on the coordinative blasting construction of both open-air slope and existing undercrossing tunnel， a numeri-cal calculation model for the coordinative construction of upper open-air slope and existing undercrossing tunnel is established withANSYS 18. 0 by taking the expansion project of a oilreservebase as the engineering background， and then the impact from the blasting construction of the open-air slope on the expanding section of the existing undercrossing tunnel is studied herein， so as toensure the stability and safety of the surrounding rock of the existing tunnel under the effect of the blasting construction of the up-per slope. The result shows that the downward-propagating initial P-wave induced by the blasting construction of the upper slopeis gradually attenuated along with the increase of the distance， and then is formed into a surface wave by the refection after itreaching the free surface of the tunnel vault， which makes the law of the downward-propagation of the surface wave increased atfirst and then decreased. Compared with that before the expanding excavation， the Z-directional peak particle vibration velocity ofthe vault of the tunnel cross-section is increased by 68. 1% after the excavation， while the peak tensile stress of the vault elementis increased by 150% ， i. e. 0. 45 MPa. In accordance with the requirement specified in “Safety Ｒegulations for Blasting”， thetunnel surrounding rock is stable under the load from the excavation blasting of the upper slope. It is suggested to arrange the con-struction sequence of the expanding section of the tunnel after that the blasting construction area of the upper slope is far awayfrom the expanding section of the tunnel. The study result has an important referential value for both the underground blastingconstruction near tunnel and the expansion project of tunnel.