Optimising freezing pipe layout for improved freezing ground within a coupled thermal-seepage field

Abstract

The formation of an artificial freezing curtain is severely constrained by groundwater seepage. Traditional numerical methods have limitations in addressing the interaction between seepage flow and freezing soil along a moving freezing front. To address this, an enthalpy-based lattice Boltzmann model is proposed to study the development of an artificial freezing curtain subjected to seepage flow. The numerical model is verified through three benchmarks: analytical solutions for phase change and convective heat transfer, and experimental test results, and is then applied to two representative configurations: a single freezing pipe and a row of three pipes subjected to groundwater flow. In both cases, seepage flow restrains the formation and development of freezing soil. For a single pipe, the development of the freeze radius is restrained the most upstream, followed by midstream and downstream. For a row of three pipes, the closure position moves towards downstream compared with when there is no seepage flow. This shift arises from the asymmetric cooling pattern induced by groundwater seepage: upstream inflow continuously supplies heat that delays freezing front advancement, whereas downstream thermal interference is weaker, allowing faster front propagation. Compared with the initial ground temperature and pipe spacing, pipe diameter has less effect on the closure position. The closure time is approximately linearly related to the water-facing length, and the slope increases with seepage velocity.