Failure mode and time-dependent reliability model of tunnel lining structure built in gypsum rock

Gypsum rock is strongly corrosive and expansive, which can cause significant deterioration in the lining structure and the strength over the life sysle of a geologic tunnel. It would seriously affect the reliability of the tunnel lining structure reliability and negatively impact complex structural rules. In this reported study, the expansion failure and corrosion failure modes of the lining structure were established according to the influence of the expansive character and the corrosivity of the gypsum wall rock on the tunnel lining structure. Based on the combined effects of swelling and the corrosivity of gypsum on the tunnel lining structure, a comprehensive failure mode for the gypsum rock tunnel lining structure was established. Based on the structural functions, a derived reliability index formula for the tunnel lining structure based on the swelling and erosion of surrounding rock was established. A reliability analysis model of the gypsum in three failure modes was instituted. Based on the failure mode of the surrounding gypsum rock, the time-dependent reliability model of Lirang tunnel was analyzed, and a rule for the reliability index in a life span over a period of 100 years was obtained. According to the calculated results, the corrosion resistance, anti-swelling and supporting structure design parameters of the tunnel lining structure of gypsum rock could be optimized, and rational maintenance and repair of the gypsum rock tunnel life-cycle was provided. The research results can be applied to reliability research of tunnel lining structures.