Thermal–Mechanical Damage Evolution During Deep Underground Excavation in Prestressed Geothermal Deposits
摘要
As deep geological formations become the new frontier for resource extraction, the arising thermal and mechanical challenges have been redefining the complexities of excavation damage management for underground engineering. To address the research gap, a novel thermal–mechanical model is thus established in this study to replicate damage evolution during sequential blasting–unloading–cooling cycle under varying stress fields and geothermal conditions. A rate-dependent plasticity framework is further developed to capture the distinct rock responses to static and dynamic loading across the broad strain-rate spectrum involved. Our findings reveal that under increasing hydrostatic geostresses, dynamic damage initially decreases due to strength enhancement but increases sharply thereafter as transient unloading becomes predominant. Subsequent ventilation then exacerbates pre-existing dynamic damage, as cooling-induced pressure relaxation draws stress states closer to failure envelope. Under non-hydrostatic geostresses, smaller lateral earth pressure (Px) implies greater radial than circumferential stress at arch crown, causing dominant vertical distribution of blast-induced damage. As Px rises, the increasing circumferential stress suppresses differential stress and hence diminishes blast-induced damage, albeit unloading damage yet becomes more significant due to greater stress localization. At the arch waist, increasing Px elevates radial stress responsible for blast-induced damage, overshadowing damage caused by transient stress-relief that shrinks progressively due to decreased stress concentration. The dynamic damage therefore transitions into a bipolar pattern as lateral pressure increases, and such bipolarity then becomes more significant during subsequent ventilation as vertical stress localization exacerbates cooling damage generation. The research findings could provide valuable insights into optimizing excavation strategies and thermal management for ensuring safe underground construction in adverse geological environments.
Highlights A coupled thermal–mechanical model is developed for damage analysis of deep excavation. Rate-dependent plasticity is proposed to capture rock behavior across distinct loading rates. Excavation damage evolution during blasting–unloading–cooling cycle is newly studied. Blasting and unloading damage during dynamic excavation is deciphered for the first time.