Failures in loess slope-tunnel system: An overview of trigging sources, acting mechanism and mitigation strategies

A profound understanding of the interaction between loess slopes and tunnels, along with the mastery of protective measures for tunnels crossing loess slopes, is crucial for ensuring the excavation and operation safety of tunnels in loess slope areas. This article summarizes research findings on the loess slope-tunnel system, concentrating on sources triggering failures, the acting mechanism of failures, and strategies for failure mitigation. Loess slopes, serving as the tunnel's bearing medium, may suffer from engineering disturbances during construction and operation, significantly affecting their stability. This is reflected in the intensification of crack formation, water infiltration, and vibration propagation in the slope. The degree of slope-tunnel interaction depends on relative spatial positioning, slope characteristics, and construction parameters. Although extensive research has focused on tunnel deformation in orthogonal systems, oblique systems require additional investigation. At different stages, preventing failure involves three levels: proactive avoidance, proactive mitigation, and passive reinforcement. Traditional approaches involve "divide and conquer," but considering tunnels and slopes as an integrated whole is an emerging research area. Innovative technologies, like Negative Poisson's ratio anchor cables and Steel-Concrete Composite Support for challenging loess terrains, are introduced. Applying these technologies in practical engineering is recommended to accumulate experience and support their mature application. This review can offer valuable support for designing, operating, and managing tunnels crossing areas prone to loess landslides.