Key Parameters Design Method of AGF Method for Metro Connecting Passage in Water-Rich Coastal Area

Artificial Ground Freezing Method (AGF) is an efficient, environmentally friendly reinforcement method for the construction of metro connecting passage in water-rich and weak stratum. The core of AGF is the design of frozen wall thickness and freezing temperature. In order to obtain the quantitative relationship between the freezing temperature and the frozen wall thickness, this study firstly equates the frozen wall to a rectangular frame mechanical model based on the stress state of the frozen wall formed by AGF. And then the calculation method of frozen wall thickness based on strength conditions is obtained by theoretical estimation. Furthermore, based on the relationship between the strength of the frozen soil and the freezing temperature obtained from the experiment, the freezing temperature and the frozen wall thickness are related to propose a frozen wall thickness design method considering the freezing temperature. In addition, experimental studies revealed that the compressive strength and shear strength of frozen soil increase linearly as the freezing temperature decreases. Secondly, the lower the freezing temperature, the smaller the frozen wall thickness required. Notably, the relationship between the frozen wall thickness and freezing temperature formed by the AGF method can be obtained through the design method proposed in this paper. Taking actual case as an example, when the frozen wall thickness is selected from 1.2 to 2.2 m, the required freezing temperature range is (-5) to (-25)degrees C. Finally, the feasibility of the designed freezing parameters in the connecting passage construction is verified through numerical simulation and field measurement, which shows that the design method has a promotion prospect.

Automated summary

The Artificial Ground Freezing Method (AGF) is an efficient and environmentally friendly reinforcement method for constructing metro connecting passages in water-rich and weak strata. This study establishes a quantitative relationship between the freezing temperature and frozen wall thickness, and proposes a design method for frozen wall thickness considering the freezing temperature. Experimental and theoretical analyses show that the compressive and shear strengths of frozen soil increase linearly with decreasing freezing temperature.