3-D STRATIGRAPHY AND ROOT GEOMETRY FROM TRENCH AND GROUND-BASED LIDAR MAPPING

摘要

Detailed 3-D stratigraphic mapping of a levee and an invading root system was performed as a part of a levee wetting front test in the north levee of the American River in Sacramento, California. The purpose of the mapping and of the wetting front test was to assess the influence of a decomposed stump in the wetting and seepage patterns within a levee embankment as part of the California Levee Vegetation Research Program. In conjunction with traditional trench logging, high-resolution (2-3 mm spot spacing) ground-based tripod LiDAR (T-LiDAR: Light Detection and Ranging) was used to develop a three-dimensional (3D) trench characterization. Repeat T-LiDAR surveys were collected as successive slices (approximately 30-60 cm thick) excavated vertically from the landside toe of the levee towards its crown. Reflective targets were placed around animal holes and roots, and metallic paint was sprayed along stratigraphic contacts such that each element could be easily identified and characterized in the infrared point cloud imagery. This allowed the creation of 3D models of the system for use in further geotechnical analyses. This paper describes the methodology and technology used to characterize the features in the trench.