Investigation on evolution law of frozen wall thickness in artificial ground freezing under seepage conditions

Abstract

Frozen wall thickness (E) is an important index that reflects the freezing performance of artificial ground freezing (AGF). In previous design and numerical studies, the inherent spatial variability of soil properties is often neglected. Moreover, groundwater seepage can remarkably affect the freezing performance in the AGF system, while the specific relations between seepage and E remain unclear. Accordingly, this study aims to explore the evolution of frozen wall thickness under seepage conditions via a numerical model that considers the coupled thermo-hydraulic process and variations in hydrothermal properties. As two vital soil properties, spatial variability of thermal conductivity and intrinsic permeability is simulated by random field combined with Monte Carlo simulations (MCs). Based on the coupled model, the effects of seepage velocity, direction, and pipe spacing are examined by sensitivity analysis. Two indicators are introduced to quantify the influences of uncertainty in hydrothermal properties and seepage. The unfavourable scenarios (i.e., lower bound) of E from random models are tabulated and formulated via evolutionary polynomial regression for practical references. These findings contribute to an enhanced understanding of the freezing behaviours of AGF and provide a rule of thumb for predicting frozen wall thickness under complex seepage conditions and design parameters.