The indoor experimental method for the microseismic issue of freezing pipe fracture and its effectiveness verification

Abstract

Artificial ground freezing technology is widely used in shaft construction in deep alluvial layers and water-rich soft rock layers. However, fractures in freezing pipes are difficult to completely eliminate. The leakage of brine caused by pipe rupture can easily trigger a degradation in the strength of the freezing wall, and even lead to flooding accidents in the well. To explore the feasibility of detecting and warning freezing pipe fractures through microseismic signals, this study constructs a physical model and experimental method for the vibration problem of freezing pipe fractures, based on the “frozen soil layer encapsulating freezing pipes (including joints)” structural type. Six types of frozen soil analog materials were first developed, with densities (2.0 g/cm³), elastic moduli (110–735 MPa), and compressive strengths (0.98–5.14 MPa) meeting the requirements for engineering frozen soil simulation. Subsequently, model freezing pipe fracture vibration tests were conducted under the encapsulation of frozen soil analog materials. The results indicate that under the constraint of frozen soil, as the radial dimension of the specimen increases, the main frequency of pipe rupture rises, while increasing the axial length leads to a decrease in the main frequency. When the radial size D = 7.5D₀ (where D₀ is the outer diameter of the freezing pipe) and the effective axial size reaches H₀ = 20D₀, the main frequency of pipe rupture tends to stabilize. By comparing the similarity criteria with the experimental results, the similarity of the freezing pipe fracture vibration problem and the reliability of the experimental method were validated. The research results lay the foundation for experimental studies and quantitative analysis of the vibration signal characteristics of freezing pipe fractures, establishing the experimental methodology and theoretical basis.