A GPR Performance Standardization Framework for Mitigation Urban Road Subsidence Risk

Urban ground subsidence represents a growing natural hazard in densely populated cities, driven by aging underground infrastructure, intensive land use, and increasing hydro-meteorological extremes. Ground Penetrating Radar (GPR) surveys are widely adopted as a preventive tool for detecting subsurface cavities beneath roadways. However, despite their widespread use, the absence of standardized performance criteria for GPR equipment has limited the consistency and comparability of survey outcomes across different urban contexts. This lack of technical standardization constrains the effective integration of subsurface survey results into preventive subsidence risk management and public decision-making processes.

This study proposes a performance-based technical framework for standardizing GPR systems used in urban road cavity detection, with the explicit aim of enhancing preventive subsidence risk management. The framework follows a three-step approach integrating hazard analysis, physical detectability, and governance relevance. First, a forensic analysis of 14 major sinkhole incidents that occurred in South Korean metropolitan areas between 2022 and 2024 was conducted to define a target cavity size associated with significant public safety risk. These observations were combined with established overburden depth–to–cavity size relationships to derive a risk-informed detection threshold, focusing on early-stage hazard identification rather than post-collapse response.

Second, minimum technical requirements for GPR systems were derived to ensure the reliable detection of target cavities under typical urban road conditions. Key parameters include center frequency thresholds based on horizontal resolution theory, operational survey speed limits required to maintain sufficient spatial sampling density, and multi-channel system configurations to ensure survey coverage and positional reproducibility. Emphasis is placed on performance outcomes relevant to hazard prevention rather than on manufacturer-specific specifications.

Third, the proposed framework was evaluated through benchmarking against international technical guidelines for near-surface geophysical investigations. This comparison demonstrates that the proposed standards are broadly consistent with global practices while explicitly addressing urban-specific constraints such as traffic conditions, spatial re-identification requirements for follow-up investigations, and administrative usability of survey outputs.

By translating physical detection capability into risk-relevant performance metrics, this framework provides a common technical reference for public agencies, survey operators, and urban risk managers. The proposed standard supports the integration of subsurface survey data into preventive urban hazard governance and contributes to strengthening the resilience of cities against ground subsidence hazards.