Pre-grouting has been widely employed in the metro construction, especially in Loess tunnels, due to the potential hazards of surface subsidence and ground deformation. In order to investigate the effect of pre-grouting in Loess, the in-situ deformation of building and surface was monitored during the tunnelling of Xi’an metro in China. Results show that the subsidence can be reduced substantially with pre-grouting to stabilize the soil ahead by setting up long pipe. Also, dividing process of measurements contributes to control subsidence in time. The ultimate subsidence is 16mm, meeting the requirements. Besides, the finite element method was used and it was found that the subsidence occurs mainly in the period of the construction of left line, which gets closer to the building. Soil excavation is the main cause of settlement and it accounts for more than 60%. Compared with in-situ monitoring, the deformation of numerical model is larger while their change trends coincided during most processes. It is noteworthy that in the advanced grouting links of actual construction, the surface has obvious uplift, which is due to soil compression caused by grouting pressure. Combined the results of field test and numerical simulation, we proposed that before the excavation of each stage, the deep pre-grouting should be employed, also the more frequent displacement monitoring of surface and tunnel must be implemented. Keywords: tunnel, water-rich Loess, pre-grouting, subsidence control

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