Single-factor analysis of influencing laws for vibration signal characteristics of freezing pipes in artificial freezing construction

Artificial ground freezing is an essential construction method widely used in underground engineering. However, freezing pipe fracture can seriously endanger overall construction safety. In this work, laboratory model tests were conducted to capture and identify vibration signals induced by freezing pipe rupture, and the characteristics and propagation attenuation patterns of such vibration signals under diverse working conditions were systematically investigated. Using a self-designed model specimen composed of steel pipe and frozen soil analog materials, the effects of external confining pressure and internal fluid pressure on typical vibration characteristic parameters, including amplitude and dominant frequency, were analyzed quantitatively. The primary objective of this study is to investigate the characteristics and propagation attenuation patterns of freezing pipe fracture vibration signals under single-factor controlled conditions, thereby filling the gap in understanding how external confining pressure and internal fluid pressure individually affect fracture signal parameters. This work extends prior studies by comprehensively considering multiple coupled influencing factors—including confining pressure, internal brine pressure, and frozen soil medium properties—that have been previously overlooked. The experimental results demonstrate that all characteristic parameters, especially the vibration amplitude, rise sharply to peak values at the instant of pipe rupture, which constitutes a distinct distinctive feature of freezing pipe fracture signals. Within the scope of the present study, the dominant frequency of rupture-induced vibration signals shows a decreasing trend with increasing external confining pressure. In contrast, the dominant frequency remains relatively stable with negligible variation as the internal fluid pressure increases. Furthermore, external confining pressure exhibits a far greater influence on the propagation and attenuation of vibration signals than internal fluid pressure, which is identified as the predominant influencing factor. In practical engineering, variations in these characteristic parameters can be used to effectively identify the fracture state of freezing pipes.