Abstract:

An open system model experiment is conducted on the pipe roof freezing and mined project of Jiangpu road station on Shanghai metro line 18 to investigate the frost heave law and control effect of freezesealing pipe roof composite structure in largescale freezing projects. Similar simulation experiments are conducted to study the freezing and frost heave characteristics of the pipe roof and the force law of the pipe roof under various influencing factors. The results reveal the following: (1) The pipe roof can restrain the frost heave well, and the pipe roof freezing and peak freezing can effectively prevent the lifting of upper soil and structure. (2) The pressure curve of the pipe roof shows regular sawtooth fluctuations with freezing time after intermittent freezing. After 3, 5, and 7 days of intermittent freezing, the frost heave pressure on the pipe roof reduce by approximately 40, 50, and 60 MPa, respectively, indicating that the method can effectively reduce the frost heave pressure. (3) The pipe roof′s frost heave pressure decreases with increasing upper pressure. Therefore, a larger upper pressure can restrain the development of the frost heave.

Key words:  pipe roof freezing, frost heave, freezing mode, similarity simulation experiment, open system