A new method of monitoring slope displacement using millimeter wave radar

Millimeter-wave radar has garnered considerable attention and found widespread application in the field of in-vehicle systems, owing to its compact size, affordability, and high precision. However, its utilization in slope deformation monitoring has been relatively limited. To address this gap, this paper undertook theoretical analysis to explore the relationship between radial displacement and spatial displacement as observed by millimeter-wave radar. Furthermore, the impact of ranging errors on planar circle solving was discussed. Subsequently, the paper established the principles for interpreting orientation information and spatial displacement, while also suggesting references for field deployment. Finally, the monitoring of displacement simulation test and engineering cases demonstrates that: 1) In millimeter-wave radar monitoring, the ratio of radial to spatial displacement follows a cosine function. Although the monitoring scale might not perfectly correspond to spatial displacement, a consistent trend between the two exists. 2) Millimeter Wave Radar exhibits the capability to monitor displacement with an error margin of 5 mm or less, accurately capturing the motion characteristics of the sliding rail. 3) A single Millimeter Wave Radar can effectively monitor a horizontal coverage of up to 200 m and acquire precise displacement information, thereby satisfying the monitoring requirements for medium-sized landslides. 4) When employing two millimeter-wave radars to simultaneously observe a corner reflector (CR, the same as below), particularly when the angle between the radar and the CR exceeds 60°, more accurate azimuth information can be interpreted. This azimuth interpretation aligns consistently with the actual sliding direction. 5) The engineering cases studies of Ehan expressway and Lu-shi expressway demonstrate that millimeter wave radar fulfills the requirements of slope deformation monitoring. The research results of this paper can provide a reference for the subsequent promotion of millimeter wave radar in the field of deformation monitoring. © Springer-Verlag GmbH Germany, part of Springer Nature 2025.