Abstract:

The vibration response and cavity effect of upper primary support and surrounding rocks of Shuidun Tunnel on ShantouZhanjiang Expressway under the effect of blasting load is studied by finite element calculation model of uppersoft and lowerhard ground based on numerical simulation method. The study results show that: (1) The vibration load of the bedrock blasting of lower part of excavation face is mainly transmitted through support structure to the arch rock; while the vibration distributions of surrounding rock ahead of upper excavation face (noncavity area) and behind excavation face (cavity area) are not symmetrical; the vibration velocity and range of cavity area are much larger than those of noncavity area, which illustrates that there is a cavity effect in the blasting vibration of tunnel in uppersoft and lowerhard ground. (2) The unidirectional confinement of the cavity is the root cause of the increase of vibration; the most unfavorable position of the vibration along longitudinal direction is about 2 m behind the excavation face; and that along the radial direction is the tangency point between contact surface of soft soil and hard soil and tunnel outer contour. (3) The vibration is mainly along radial direction, i.e. the vibration of crown top of surrounding rock is mainly along vertical direction and that of arch foot (arch springing)of primary support is mainly along horizontal direction. (4) The crown top of surrounding rock and arch foot of primary support are the key points to control blasting vibration where is 1D,where D is tunnel diameter, away from excavation face.

Key words: tunnel, soilrock interlaced strata, blasting vibration, vibration response, cavity effect, numerical simulation