Abstract:

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.

Key words: highway tunnel, water conveyance tunnel, vibration influence, numerical analysis, site monitoring