New Framework Integrates Remote Sensing for Urban Ground Settlement Detection

Ground settlement, the downward movement of the earth's surface, poses increasing risks in urban areas due to extensive underground development, particularly threatening infrastructure like subways. Conventional monitoring methods often lack the wide-area coverage or depth penetration needed for reliable assessment. For instance, GPS is ineffective for underground structures, while satellite-based Interferometric Synthetic Aperture Radar (InSAR) can be complicated by atmospheric conditions and observation geometry.

A research team from Seoul National University of Science and Technology has developed a forensic multi-scale remote sensing (MSRS) framework to address these limitations. This innovative system integrates InSAR for wide-area, long-term settlement detection, laser scanning (L/S) for site-specific structural validation, and ground-penetrating radar (GPR) for near-surface condition assessment. The fusion of these technologies aims to not only detect settlement but also investigate its underlying causes, such as excavation issues or construction defects.

The MSRS framework was tested along a 16-kilometer section of the Seoul Metropolitan Subway Bundang Line. Initially, satellite InSAR analysis identified a ventilation shaft with a distinct long-term settlement signal, excluding seasonal fluctuations. Subsequent field L/S at the shaft revealed cracks and signs of repair on the ceiling, with settlement patterns becoming more pronounced towards the area directly beneath the roadside above the shaft.

Following the L/S findings, GPR was employed along the road section above the shaft. This non-destructive technique indicated void-like structures and reduced subsurface layer continuity, suggesting nonuniform conditions. The integrated visualization of data from all three techniques confirmed the detected settlement anomaly as a reliable result, reducing the uncertainty associated with relying on a single monitoring method.

This research proposes a shift from reactive urban disaster management to proactive prevention. The MSRS system is expected to support timely maintenance and targeted investigations of high-risk areas, thereby mitigating the dangers of sinkholes, structural damage, and infrastructure failure. By facilitating early detection of ground-related risks and warning signs, the system aims to prevent hazards from escalating into serious issues.