Research On Over-or-under Excavation Control Of Tunnels In Tuff Layer With Developed Cutters

The Ⅲ level surrounding rock of ShiLang Mountain tunnel inclines and factures seriously, since the traditional smooth blasting excavation causes extensive over-or-under excavation phenomenon, the blasting effect far from ideal, brings tunnel construction with adverse effects. According to the cutters development conditions of the surrounding rock, on the basis of smooth blasting, the cutting seam pipe orientation fracture blasting device developed, in order to guide the blasting energy priority to release from the relative complete part of surrounding rock, then control the over-or-under excavation effect. The main content of this article includes:(1) A lot of literature can be turn to when blasting technology (including smooth blasting, the pre-splitting blasting and orientation fracture blasting) is wanted, then a summary of the present research situation presented.(2)This paper discusses how rock joints influence the blasting effect, based on directional fracture formation mechanism, crack propagation conditions, crack propagation direction, the technical characteristics of crack tube orientation fracture blasting, the cutting seam pipe directional amplitude fracture blasting device created.(3)Rely on ShiLang mountain tunnel project, according to the serious geological situation of the III level tunnel surrounding rock cutters fracture, the in-site blasting test executed. Then compare the traditional smooth blasting method with vault cutting seam pipe orientation fracture blasting method in the same section in tunnel. The peripheral hole forming quality, over-or-under break situation are considered, also the blasting parameter optimization design completed, and put forward the blasting control measures in ShiLang mountain tunnel with cutters development and tuff formation geometry, etc.(4)Summarizes the properties of accumulated energy directional breaking blasting technology by analyzing it’s mechanism and field the blasting test work. And this provide some theoretical guidance for determining reasonable blasting design parameters.