Abstract
This paper proposes an explicit scheme to analyze the failure of a subsea polyhedral tunnel-liner system with an inverted arch under mechanical loading and fire fields. The thin-walled liner is made of Functionally Graded Materials (FGMs),which may improve the stability behavior of the tunnel-liner system. Hydrostatic pressure is inevitable in the liner since underground water may penetrate the cracks of the tunnel,and reach the outer surface of the liner. In addition,an elevated temperature loading is taken into account,considering that fire may occur in the tunnel-liner system. Under the combination of mechanical loading and thermal loading,the liner deforms into a single-lobe shape,which is depicted by a trigonometric function. The total potential energy is expressed quantitatively after the energy approach and thin-walled shell theory are used. The minimum potential energy is obtained when the critical buckling occurs. The critical buckling pressure is calculated,which considers the effect of the thermal field. The present analytical prediction is subsequently compared precisely with other closed-form solutions. Finally,the effects of several parameters,such as the geometric shapes,temperature variations,and volume fraction indices,are discussed to further survey the buckling performance of the nonlinear buckling of an FGM polyhedral liner with an inverted arch. One may address a polyhedral liner with fewer polyhedral sides,and a lower volume fraction index is recommended to rehabilitate cracked tunnels in engineering applications.
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