Abstract
The use of digital elevation models (DEMs) that use airborne-based light detection and the ranging technique (airborne-based LiDAR) to understand large-scale geological structures has become important in geological surveying and mapping. Taking the Dongao Tunnel area in northeastern Taiwan as the study area, this study used the airborne-based LiDAR DEM and related value-added maps to interpret the topographic and geomorphic features of the area and identify locations for geological investigation. The characteristics of the rock mass were observed on-site and revealed by excavation of the highway tunnel in the study area; they were compared with the interpreted topographic and geomorphic features to determine the potential of using 1 m-resolution LiDAR DEM in geological surveys and in the evaluation of engineering characteristics of underground rock masses. The results of this study demonstrated that the DEM accurately captured geomorphic features: the strata composed of slate and schist had distinct appearances in both the clinometric map and the hillshade map; the locations of faults, lineaments, and drainage were consistent with those observed on-site, and the positions of these features were captured more accurately than those on conventional maps. Evident microrelief features, including the distribution of scarps, erosion gullies, and mini-drainage systems provide an effective basis for interpreting a deep-seated gravitational deformation slope and for an on-site inspection for validation. The use of high-resolution LiDAR DEM to interpret geomorphic features along with geological surveys provides a more comprehensive understanding of the survey area, supporting surveys and geological mapping, revealing the locations of potential slope failures, and enabling the assessment of tunnel engineering risks.
Highlights
Topographical and geological investigations are essential in every stage of the life cycle of an infrastructure; these stages are the feasibility study, planning, design, construction, operation, and rehabilitation
The geomorphic features that were interpreted from clinometric maps and hillshade maps generated from high-resolution airborne-based light detection and ranging (LiDAR) digital elevation models (DEMs) were divided into three groups: stratum and lithology, fault-related, and scarp and slope deformations, as described below
Based on the geological information that was revealed by tunnel excavation, this section discusses the application of the fine geomorphic information that was obtained from the airborne-based LiDAR DEM in the geological survey and mapping
Summary
Topographical and geological investigations are essential in every stage of the life cycle of an infrastructure; these stages are the feasibility study, planning, design, construction, operation, and rehabilitation. Results of such investigations affect the selection of alignment and method of construction and provide important information concerning factors that affect structural deterioration or damage and associated maintenance measures [1,2,3,4]. Fine topographical data are frequently used to estimate the extension of different rock layers, to determine the existence of geological structures, collapsed areas or the spatial distribution of deep-seated gravitational deformation slopes and to provide a basis for the interpretation of the results of geological surveys
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