Ground temperature characteristics during artificial freezing around a subway cross passage

Artificial ground freezing (AGF) has been extensively used in the construction of subway cross passages in soft ground to ensure the safety of excavation. The temperature characteristics during freezing are of great interests, as it can be used to determine whether the frozen wall satisfies the design requirements in terms of dimension and strength. This paper presents a detailed case study of a cross passage including the temperature variations in brine and selected monitoring points around the passage based on the field testing results during freezing and frozen wall maintenance. In particular, temperature data was collected at various depths along settlement observation holes installed on top of the frozen wall. It was found that the frozen wall development rate toward the cross passage is 1.43 times faster than that away from the passage in the silt. A three-dimensional numerical model was used to analyse the temperature distribution and was able to accurately reflect the temperature distribution within the entire frozen zone with uneven distribution of the freezing pipes during freezing. This paper provides a valuable case study of the temperature characteristics of a cross passage with uneven freezing pipe distribution and a thermal model with complete thermal properties at both frozen and unfrozen status, which can be useful for thermal model calibration and/or temperature field prediction in artificial freezing engineering.