In-plane stability of an underground support system with steel corrugated webs: Experimental study, finite element analysis, and design formula

This study proposed an innovative underground support system with I-shaped sections that use steel corrugated webs. The in-plane global buckling behavior of the proposed system was investigated through comprehensive experimental, numerical, and analytical analyses. An experimental test was carried out against a scaled specimen of the proposed support for U-shaped mining roadways when subjected to three concentrated loads. The global asymmetric buckling was identified as the ultimate failure mode. A finite element (FE) model was constructed and verified by comparing its analysis results with the experimental outcomes. Finite element analyses (FEA) first proved that both the stiffness and force capacity of the support with corrugated webs could be much increased when compared with the I-shaped steel that uses flat webs under the same steel consumption. The elastic and elastoplastic buckling analyses from the FEA further indicated that the web height and flange thickness were the influential parameters, from which a closed-form formula was developed to predict the elastic buckling load as a function of the slenderness ratio. Analysis results have shown that the support system will inevitably fail through antisymmetric instability when the slenderness ratio is large, yet the system was not very sensitive to initial imperfections. A design formula for the in-plane compression-bending capacity was derived for the proposed support system by synthesizing and modifying existing relevant design equations. The proposed innovative support system, together with the associated experimental testing, FEA, elastic buckling load formula, and design equation, paves the way to promote its real-world applications as tunnel supports to deal with harsh geological conditions (e.g., soft rocks).