Abstract: With the tunnel segment of Xi'an Metro Line 5 as engineering background, we examined and compared the ground settlement, soil deformation around the tunnel, and mechanics effect of water-rich loess tunnel reinforced by different methods (dewatering reinforcement and grouting reinforcement) via a seepage-stress coupling numerical model. We further validated the numerical result according to site monitoring data. Results demonstrated that the maximum ground settlement of the tunnel strengthened by dewatering reinforcement was 13.7 times that by grouting reinforcement. The laws of soil deformation around the tunnel under these two reinforcement schemes were consistent, and the deformation value of surrounding rock in ten days of excavation reached about 70%-80% of the stable value. Soil around the tunnel suffered from compressive stress under grouting reinforcement, while tensile stress appeared in the soil layer of the middle wall and the middle plate during the excavation under dewatering reinforcement. The stress of the lining under grouting reinforcement was larger than that under dewatering reinforcement. The extreme value of plastic zone under dewatering reinforcement was 11.3 times that of grouting reinforcement, mainly distributing at the shoulders, waists and feet of the arch on both sides. The simulated values of ground settlement and soil deformation around the tunnel under the two reinforcement schemes were similar and basically consistent with the change law of the monitored value.

Key words: water-rich tunnel, strata deformation control, dewatering reinforcement, grouting reinforcement, numerical simulation, on-site monitoring