Reliability Studies On Segment Component Of Shield Tunnel Under Fire

Abstract:With the development of urban rail transit in our country, and the advancement of the shield construction technology, more and more traffic tunnels are built by the shield method. At the same time, the security issues are increasingly becoming attention by people, and the tunnel fire is one of the major problems concerned. Previous tunnel fire cases show that tunnel fire will not only cause significant casualties and property losses, but also will cause serious damage to tunnel lining structure. Shield tunnel is mainly composed of the segment component. The fire will cause serious damage to it, so the segment structure bearing capacity and safety greatly reduced; besides, there is uncertainty with the shield tunnel in design, construction, and operation, how to evaluate the bearing capacity and security of the segment structure of shield tunnel under fire accurately and quantitatively, became a important question in the fire resistance research of shield tunnel. In this paper, which was on the basis of previous studies and takes the real project as the background, the theory of structural reliability was adopted to analyze the effect of fire on the segment structure. The main work as follows:(1) According to results of fire test at home and abroad, the fire heating curve and concrete thermal parameters were selected, and then through the finite element software ABAQUS calculated the temperature field of the segment component, and analyzed the cross-section damage law from the point of view of material under high temperature.(2) Based on the equivalent cross-section method, the ultimate bearing capacity formula of the segment component section with the time of fire was given; then combined with the routine method which calculates the internal forces of shied tunnel, established the function of the segment component under fire.(3) Using the FOSM method, the reliability of the segment component under fire was calculated, and analyzed the reliability law of the segment component with time under fire in different factors such as concrete, steel grade, shield tunnel depth ect.(4) According to the reliability law of the segment component with time under fire, assessed the security of segment component, and suggested the reliability index of the shield tunnel segment structure after fire, and proposals of fire resistance and fire protection design.