Abstract:

The Tianhe Station horizontal frozen construction in Guangzhou metro No.3 line is the longest and biggest artificial ground freezing (AGF) project of the national metro construction currently. In the different phases of the construction; several parameters such as brine temperature, ground temperature, surface settlement/heave, swelling pressure, tunnel liner convergence and so on, are monitored dynamically. According to the data obtained from about 400 days in-situ monitoring, the features of propagation speed of the frozen soil wall and the brine temperature variation are discussed. The characteristics of ground temperature and the swelling pressure of soil are analyzed. The relationship between the ground pressure and the soil temperature is also achieved. Results show that the temperature gradient variation and soil temperature variance ratio decrease with the increasing of freezing time in the active freezing phase. The safety of frozen earth wall is also evaluated by different monitored data. Moreover, the environmental influence of the project is evaluated based on the surface frost heave and settlement data monitored in the process of construction. It is found that the pre-freezing time is too long which induces large surface frost heave and increases the project capital cost. The analytical results show that the pre-freezing time should be reduced.

Key words: horizontal frozen, metro, monitor, frost heave, freezing temperature, frozen wall