Experimental Study on Frost Heave Characteristics of Silty Clay Beneath Operating Stations in Twin Tunnel Freezing

Artificial ground freezing method construction is widely applied in the subway construction in Shanghai. In the project of the twin tunnel freezing method crossing the operating Line 10 station at No.18 Guoquan Road in Shanghai, the tunnel is located in the silty clay with a water content of 38.5%. The frost heave pressure of the silty clay will cause uplift and even cracking of the already operating station. Taking the Shanghai silty clay as the research object, this study investigates the influence of the cold end temperature and conductive temperature on the frost heave pressure of the soil through laboratory frost heave experiments and similar simulation experiments. The results show that under closed freezing conditions, there is a good linear relationship between the frost heave pressure of the silty clay and the cold end temperature, while under open freezing conditions, the frost heave pressure of the soil has a quadratic relationship with the temperature difference of the soil under the structure’s base plate. The research findings will provide valuable references for projects such as the freezing method for crossing operating stations and existing lines in Shanghai subway construction.