Abstract:

The shield for the 3rd section of No. 1 line of Zhengzhou Metro passes underneath an oil station, which has three underground parallel oil tanks. With a total capacity of 150 m3, the oil station belongs to Grade I oil station. The vertical and horizontal distances between the left tunnel tube and the three oil tanks are 7.0 m and 2.7 m respectively. The oil station belongs to Grade I risk resources. In the paper, countermeasures are proposed for the shield tunneling so as to ensure the tunneling safety. The settlement induced by the tunneling of the shieds is simulated with ANSYS program, and the maximum cumulative ground surface settlement and inclination ratio calculated have not reached the alarm values. Therefore, the oil station can be in normal service during the shield tunneling, but field monitoring should be strengthened and emergency measures be formulated. Countermeasures in term of lagging distance between the two shields of the twintube tunnel, the pressure in the excavation chamber and the grouting pressures are proposed so as to ensure the safe tunneling of the shields. The monitoring of the settlement of the ground surface and the buildings (structures) during the shield tunneling shows that the maximum cumulative settlement and the settlement rate have not reached the alarm values. So far the shields have already passed the oil station successfully. The paper can provide reference for similar projects in the future. 

Key words: Zhengzhou Metro, shield, settlement, numerical simulation, monitoring, oil station