Evolution Law of Three-Dimensional Non-Uniform Temperature Field of Tunnel Construction Using Local Horizontal Freezing Technique

Abstract

The formation quality of a frozen wall is one of the prerequisites for tunnel excavation using artificial ground freezing techniques. However, the non-uniformity of temperature distribution along the length direction of the freezing pipe is often ignored in the actual freezing engineering, which leads to a thin frozen wall at a local position that does not meet the design requirements. Therefore, exploring the evolution law of three-dimensional non-uniform freezing temperature fields is necessary. In this paper, a tunnel horizontal freezing model test system was established based on the similarity criterion of hydro–heat coupling, and the temperatures at three sections were tested using thermocouple temperature sensors. The results show that the temperature drop curves of measurement points suffer from three periods: steep drop, slow drop and tending to be stable. The temperature curves on the main and vice planes of the frozen wall all present a “V” type; specifically, the temperature on the axis plane is the lowest, while the temperature away from the axis plane is higher, and the temperature gradient outside the axis plane is greater than that inside. The frozen wall develops from frozen soil columns to a sector ring, and the average thickness of the frozen wall at three sections is 50.6, 40.7 and 75.1 mm after freezing for 60 min, respectively, which shows an obvious non-uniformity. The temperature distribution along the length of the freezing pipe is T = −0.000045z2 + 0.0205z − 13.5125. The freezing temperature contours calculated by ABAQUS are basically consistent with those calculated by the model test after calling the temperature function of the freezing pipe wall.