Wholistic Monitoring—Integrated InSAR, Lidar, and Instrumentation

Interferometric synthetic aperture radar (InSAR), light detection and ranging (lidar), and instrumentation have been tools in the geotechnical engineer’s toolbox for decades. However, these technologies have experienced improvements and cost reductions on vastly different timelines; therefore, engineers have generally employed these technologies separately for evaluations and long-term monitoring. Individually, these technologies provide unique benefits for a given project, but combined these technologies provide a holistic view of a geotechnical asset. Satellite InSAR systems, such as the European Space Agency’s Sentinel-1, provide a nearly temporal continuous picture of past and present movements in many discrete locations on and around an asset. Tripod-mounted lidar provides a spatially continuous 3D point cloud of assets at discrete points in time using the laser time-of-flight principle. Lastly, instrumentation, such as tiltmeters and shape arrays, provides automated continuous monitoring of movement on an asset at specific locations. Here, we present an example of a vertically integrated workflow using InSAR, lidar, and instrumentation for monitoring retaining wall performance. This study includes monitoring of several mechanically stabilized highway retaining walls in the southern region of the United States. The proposed workflow combines the three technologies to overcome their individual limitations and provide spatially and temporally continuous asset monitoring. For example, the long-standing challenge of locating a few high quality tiltmeters in the most significant areas of concern is partially answered by identifying wall locations that exhibit geometric anomalies in the lidar point clouds. Additionally, evaluating regional historical and ongoing InSAR trends and local automated instrumentation data helps inform the frequency of subsequent lidar scanning. When vertically integrated, these tools allow for the data-driven selection of the frequency and extent of future monitoring and inspections. This approach allows engineers to tailor the monitoring program to each asset’s performance and enables owners to allocate limited inspection and maintenance resources more efficiently.