3-D Voxel Modeling of Near-Surface Sediments: Insights into Depositional Environments and Geotechnical Properties- A Case Study of Barishal Town and its Surroundings, Bangladesh

Abstract

Geology is a natural science focused on understanding the Earth’s composition, structure, and processes. 3D geological modeling effectively visualizes complex surface and subsurface conditions, geological settings, and geomorphic processes. This technique provides near-realistic representations of geological features, making them easier to understand for both professionals and the public compared to traditional maps and diagrams. This study integrated geological, geotechnical, and special datasets within a GIS framework for statistical analysis.  Key datasets include sand-silt-clay percentages, SPT-N values, litho-coarseness curves, core photographs, geomorphological features, and depositional domain maps. The geomorphic features of Barishal town and its surroundings are characterized by complex and dynamic fluvial-deltaic systems. 97 geotechnical boreholes, covering approximately 94 km², which were analyzed to construct a 3D geological model down to a depth of 30 meters. 3D indicator kriging, a geostatistical method, was used to create a voxel-based geological model (100m x 100m x 0.50m). Each sediment layer was assigned to cluster IDs for a second round of 3D indicator kriging, visualizing sediment-type clusters, sequences, and depositional stages from younger to older sediments. The domain map provides additional insights into the depositional history. The voxel model can be explained through thickness maps, unit-wise visualization, and depth-wise slicing. The thickness map shows sediment accumulation and depletion. The unit-wise voxel model presents six depositional sequences in the study area from younger to older stages with lithological assemblages. The sediment assemblages could be displayed in six different depth levels: at the surface, 5m, 10m, 15m, 20m, and 25m, relative to mean sea level (MSL), showing a fining-up trend. Automatically generated cross-sections clarify lithological variations and sediment interlayering. 3D model enhances scientific understanding and improves communication among engineers, planners, and non-specialists by translating complex geological data into intuitive visuals. This approach supports informed decision-making and resilience planning while aiding geoscientists in analyzing subsurface conditions related to groundwater quality, pollution, and paleo-flood predictions.