Experimental thermal behavior of sandy gravel stratum during artificial ground freezing-thawing process under seepage flow

Artificial ground freezing faces challenges under groundwater seepage. This study experimentally investigates thermal evolution in water-rich sandy gravel strata during freezing and thawing processes. Results show that 34.6 m/d seepage extends frozen wall closure to 175 min, with the vault and upstream sidewall becoming critical weak zones failing design requirements. Forced thawing reduces duration by 83.1% compared to natural thawing. Under coupled seepage and forced thawing, a dual-directional thawing mechanism is observed. The upstream zone thaws faster, suggesting that terminating heating in upstream pipes early can optimize energy efficiency. These findings provide quantitative benchmarks for underground engineering in high-seepage strata.