Study of backwater prediction and foundation safety risk analysis along the Metro

Metro engineering is a key approach to relieve the pressure of urban surface transportation. However, the intrusion of metro engineering into aquifers may lead to a high risk of groundwater level rising, with the accelerated development of urbanization in China, it is essential to clarify this risk and further assess its impact on the bearing capacity of shallow foundation. In the study, a three-dimensional numerical model coupled linear metro engineering structure was constructed through numerical simulation methods, the groundwater level rising values along the typical section of Jinan Metro Line 4 was calculated in the short and long-term scenarios, the range of groundwater level rising was predicted under short-term scenario and the impact of groundwater level rising on the bearing capacity of shallow foundation along the metro line was calculated. The results indicated that: 1) The numerical range of groundwater level rising along the metro line after 1, 3 and 10 years of simulation is 12.942~24.839 cm, 5.117~17.890 cm, and 2.291~7.869 cm, respectively. The groundwater level rising value decreases to a lower degree after 10 years of simulation, confirming that the long-term impact of the engineering structure on the regional groundwater flow field tends to be weak; 2) In the short-term one-year scenario where the backwater effect is more obvious, the backwater value of groundwater along the research section of rail transit line 4 in flood season ranges from 16.949 cm to 29.077 cm, which is 4.667 cm higher than that in non-flood season.3) The backwater phenomenon is distributed along the line and can be divided into two obvious main backwater zones. The reduction rate of foundation bearing capacity affected by backwater is 0.186%~0.589%, and the influence of groundwater backwater on foundation safety is relatively insignificant. Based on the innovative understanding of the influence of groundwater backwater along the linear subway project, the study will provide theoretical support for solving geological environmental risks in the planning and construction of Jinan Metro Line 4.