Abstract

Purpose: This study analyzes structural risks during temporary earth-retaining structure (TERS) dismantling and examines the limitations of monitoring-based safety management, focusing on a fatal H-pile dismantling accident at a railway subgrade construction site in Dangjin, Chungnam Province, Korea (August 2019). The research particularly investigates structural re-equilibration, load redistribution during brace removal, and the linkage between monitoring anomalies and failures in work-stoppage decision-making. Results: The analysis confirms that, in the Dangjin case, after sequentially cutting seven of eight welded connections between the H-pile and the waler, the final remaining joint could not withstand the highly concentrated load, fractured spontaneously, and caused the waler (H-300×300) to topple and fatally strike a worker. The accident represents a typical failure of structural re-equilibration, as no prior review of load-transfer paths for each cutting sequence had been conducted and no dismantling work plan had been prepared. In addition, although monitoring anomalies during dismantling can function as precursors to progressive collapse rather than simple displacement trends, these signals were not linked to any formal work-stoppage procedure, allowing the risk to escalate. Conclusions: This study conceptualizes TERS dismantling as an independent structural transition phase characterized by intensive structural re-equilibration and nonlinear load redistribution. It highlights the need for rate-of-change-based risk management criteria and for a monitoring-to-decision linkage system that explicitly connects monitoring anomalies to timely work-stoppage decisions in dismantling operations.