Development of a Multi-Scale Packing Methodology for Evaluating Fate and Transport Processes of Explosive-Related Chemicals in Soil Physical Models

摘要

The development of the scalable systems and methods involves proper reproduction of soil composition, lithology and structures, appropriate placement of boundary conditions, suitable simulation of representative environmental conditions, and the use of representative sampling systems. This paper evaluates the effect of different packing methods with a tropical sandy soil for obtaining a uniform and homogeneous packing so that these characteristics are comparable across all scales and dimensions. The packing methods used include piston-driven dry packing, piston-driven wet packing, and gravity-driven sedimentation packing. For dry and wet packing, the procedure consisted on the iterative addition of soil layers, mixing and compaction. Sedimentation packing involved the preparation of soil slurry and allowing its deposition under gravity. The systems were evaluated for consistent bulk density, porosity, homogeneity, and soil dispersivity. Preliminary results exhibit satisfactory bulk density and porosity values for the piston-driven methods, ranging from 1.59 to 1.64 g cm~(-3) and from 42 to 44%, respectively. Sedimentation packing results in fair homogeneity and gradation, while dry packing develops heterogeneous layering. Transport parameters were also evaluated resulting in consistent dispersivity values for wet piston-driven packing ranging from 0.09-0.19 cm. Wet piston-driven packing is recommended as they yielded the most reproducible results for tropical sandy soils. The reproducibility of the recommended method is tested and proven in other physical models of different scales and dimensions. The method herein developed are, therefore, applicable for the development of representative multidimensional physical models designed to simulate soil and environmental fate and transport processes occurring in field conditions where landmines and other explosive devices are present.