Abstract:Close-range construction using the artificial ground freezing (AGF) method beneath existing subway structures may induce deformation, posing potential threats to operational safety. In response, this study analyzes the principle of differential settlement measurement using electro-level beam sensors and develops an automated monitoring system for subway structural settlement based on this technology. The system was applied in a practical engineering project involving AGF-based underpass construction beneath an operational subway station. Monitoring results revealed a significant linear correlation between electro-level output angle and temperature. After temperature correction, measurement accuracy was substantially improved. Whether using a single electro-level or a multi-point chain configuration, the monitoring results were consistent with conventional leveling trends and demonstrated higher precision than manual leveling. By applying closure correction from manual leveling, the electro-level data were further refined, enabling accurate tracking of structural settlement during construction. The system offers effective technical support for similar engineering applications.
