ABSTRACT
This paper presents a detailed case study of operating high-speed railways that were undercrossed by two metro tunnels in a loess region. The intra- and post-construction effects of shield tunnelling on the settlements of overlying subgrade and railways are analysed. Automatic monitoring technologies were employed to record the deformations of railway structures, strati-fied settlements of the subgrade during and after the tunnelling periods. The findings demonstrate that the four railways undercrossed by metro tunnels undergo significant uneven settlements and display analogous deformation troughs over time. The settlement peaks occur above the two metro tunnels, with a maximum settlement of 3.39 mm when the crossing is completed. The pri-mary settlements are concentrated in the deeper soil layers in the vicinity of the newly constructed tunnels, while minor consolidation displacement is observed. This pattern suggests that the pri-mary cause of continuous settlement is soil loss due to tunnelling. The railway experiences post-construction settlements that are approximately 0.63 times those of the subgrade at corresponding locations, demonstrating the railway's greater resistance to uneven settlement, primarily due to its continuous structure. The post-construction settlements of subgrade and railway approach -3.31 and -2.12 mm after 400 days, respectively, according to the prediction model. This case study provides essential guidance for short- and long-term monitoring and maintenance of high-speed railways.
