Estimation of Excess Ice and Thaw Settlement in Frozen Soil Using Industrial Computed Tomography

ABSTRACT Permafrost thaw can induce terrain instabilities and hazards as a result of the loss of excess ice from host sediments. The loss of excess ice threatens the integrity of infrastructure and drives ecosystem changes across northern landscapes. This study tests a nondestructive approach to estimate excess ice and potential thaw settlement using industrial computed tomography (CT) and compares it with traditional destructive methods. We developed a reusable 3D‐printed thaw settlement chamber suitable for CT scanning and created controlled synthetic permafrost cores from Devon silt (~25% clay, < 5% organic content) where input water volumes were precisely known. Cores were scanned before and following thaw, while supernatant water released during thaw was measured. Thaw settlement ranged from 27% to 76% of original core height across the four cores tested. We show that CT‐derived excess ice estimates closely match the supernatant water released during thaw, demonstrating effective nondestructive quantification of excess ice via 3D CT scanning. CT‐derived excess ice content (EIC) estimates are within 1.7% of measured thaw settlement compared to 4.4% for destructive EIC methods. The approach to estimation of excess ice and thaw settlement in this paper is relatively simple, without loading, sample agitation, or remolding, as used in some previous studies, yet shows strong congruence between visible ice content, excess ice, and thaw settlement across both destructive and nondestructive methods. We find that both CT and simple destructive approaches can reliably estimate potential thaw settlement in simple sediment‐ice mixtures and provide a framework to understand relations in more complex sediment mixtures.