Research On The System Of The Tunnel Blasting Design And The Problem Of Over-break As Well As Under-break

The tunnel and underground engineering can effectively alleviate the congestion status of ground traffic, so in recent years, more and more the form adopted in the project of underground tunnel. This paper mainly studies two aspects about the tunnel, one is the study of tunnel blasting and tunnel blasting design system, the other is the influence of surrounding rock and initial support caused by over-break or under-break during tunnel construction.Through the study on blasting excavation construction method of tunnel, Using computer software to design a tunnel blasting design system. In this paper, adding the internal control to build a tunnel excavation design interface by the Visual Basic 6.0, to achieve the various controls function on the use of VB language. After entering the geological parameters and blasting parameters of a tunnel, editing the code, setting properties for each control to calculate the related parameters of blasting design, then output the results. On the basis of the output results and tunnel design parameters, using VB drawing function to draw the blasting network diagram.As a result of tunnel blasting construction often appear over-break and underbreak, while the existence of over-break and under-break can affect the mechanical properties of initial support. In this paper, by using the finite element software, Ansys11.0, under the condition of over-break and under-break of initial support were simulated, with no over-break and under-break in case of initial support for comparative analysis that, in actual engineering construction, should control the vault to the arch shoulder part of the over-break, strictly limit the under-break of side wall portion; over-break and under-break of shoulder portion has adverse effect on the initial support structure of arch tunnel.