Floor heave failure mechanism and remediation measures in operational dolomite-gypsum interbedded tunnels: A case study

Groundwater erosion of gypsum-bearing rock surroundings triggers the expansion of the plastic zone and the leaching of sulfate ions, weakening the surrounding rock and further corroding the concrete lining in high- speed railroad tunnels, which ultimately floor heave. This paper investigates the failure mechanisms of floor heave in the L tunnel by combining in-situ stress tests, field groundwater level monitoring, core drilling test data, and stratification monitoring. The degree of influence of basal surrounding rock deterioration and concrete corrosion on floor heave disease is revealed through numerical simulation methods. The results show that the dissolution of gypsum in the surrounding rock, driven by groundwater seepage, weakens its strength and contributes to the formation of fissures. The sulfate ions released from gypsum further corrode the concrete, reducing the support capacity of the inverted arch. The coupled effects of surrounding rock deterioration and concrete corrosion accelerate the deformation process. The study highlights that basal surrounding rock deterioration is the primary factor driving floor heave, while sulfate corrosion exacerbates deformation over time. A 6 % basalt fiber (BF) dosage improves the concrete's resistance to sulfate corrosion, offering a solution for mitigating floor heave. These findings provide valuable insights into the geological mechanisms behind tunnel failure in gypsum-bearing strata and offer practical recommendations for tunnel engineering in chemically aggressive geological environments.