Abstract

Sudden rupture of freezing pipes frequently occurs in artificial ground freezing engineering. Owing to complex field environments, it is difficult to clarify the single-factor evolutionary laws of vibration signals induced by pipe fracture through field monitoring. Four groups of model freezing pipes with diameter-to-thickness ratios ranging from 20 to 26 were fabricated through geometric scaling based on engineering prototype pipes of Φ140 × (5–7) and Φ159 × (6–8). A low-temperature brine medium at −30 °C was circulated inside the pipes to simulate actual in situ refrigeration conditions. A series of tensile rupture tests were performed to explore the vibration response characteristics of freezing pipes with different specifications. The test results indicate that the ultimate rupture load is positively correlated with signal energy. Within the diameter-to-thickness ratio range of 20–26, the signal amplitude decreases approximately linearly (R2 = 0.99), while the progress count and signal energy increase gradually, and the dominant frequency of rupture vibration signals decreases continuously. In other words, the dominant frequency gradually declines as the diameter-to-thickness ratio rises. Unlike conventional acoustic emission characteristics of bare steel fracture, which are typically characterized by high-amplitude, high-energy bursts with prominent central frequencies, the vibration signals of freezing pipes surrounded by frozen soil exhibit significantly lower dominant frequencies (3–30 kHz), rapid attenuation due to pipe–soil energy radiation, and a frequency shift that is structurally governed by the diameter-to-thickness ratio rather than by material properties alone. The quantitatively established frequency bands and parameter evolution patterns can serve as reference criteria for field monitoring and early warning of freezing pipe fracture in artificial ground freezing engineering.

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