Abstract: Composite linings are often adopted in highway tunnels. The new Austrian tunneling method is used in tunnel’s designing and construction. For weak wall rock section, steel arch(or grid arch) + grouting + shortcrete network of united initial support form are adopted. The key to achieve dynamic design is to find a good method to evaluate initial support safety evaluation about shape steel reinforced shotcrete. This paper gives a systemic study on initial support safety evaluation and established a numerical calculation method. Firstly, according to the monitoring data, this paper analyzes the final settlement value and horizontal constringency of wall rock and makes it as a basis for parameter inversion. Secondly, adopting the mechanical parameters from inversion, the initial support internal force about shape steel reinforced shotcrete is calculated by stratum-structure numerical method. Finally, initial support safety is calculated and evaluated by safety factor calculation method of shape steel reinforced shotcrete. From the study of this paper, we find that the initial support of shape steel reinforced shotcrete can exert the strong support effect of shape steel. And that, when the shotcrete is upgraded, concrete plays a major supporting role. The space between shape steels is not prominence in increasing the initial support safety factor.

Key words: shape steel reinforced shotcrete, highway tunnel, initial support, safety factor