Abstract:

With 120 m2 crosssection area, Fengning tunnel has 4 063 mlong section located in Grade Ⅱ surrounding rock. In the paper, two parallel cuthole schemes, i.e., scheme with the central holes being empty and scheme with the surrounding holes being empty, for the Grade Ⅱ surrounding rock section of Fengning tunnel are simulated by means of ANSYS/LSDYNA finite element program, and the transmission rules of the blasting stress waves and the rock destruction conditions are analyzed, which concludes that the scheme with the central holes being empty is the favorable scheme; appropriate parameters are determined for the contour holes on basis of the smooth blasting technology; the blasting effect is assessed on basis of the field observation data. Conclusions drawn are as follows: 1) The design of "parallel cut hole with the central holes being empty+appropriate blasting parameters" is rational; 2) The numerical simulation technology can reduce the cost effectively. The study result can provide reference for similar projects in the future.

Key words: large crosssection hard rock tunnel, numerical simulation, parallel cut, smooth blasting