Geotechnical centrifuge testing of LNAPL migration in vadose zone with heterogeneity

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Authors:Kawabata, Junichi; Soga, Kenichi; Coumoulos, Helena; Kechavarzi, Cedric
Author Affiliations:Primary:
2-19-1 Tobitakyu, Chofu City, Japan
Cambridge University, United Kingdom
Volume Title:Geological Society of America, 2000 annual meeting
Source:Abstracts with Programs - Geological Society of America, 32(7), p.186; Geological Society of America, 2000 annual meeting, Reno, NV, Nov. 9-18, 2000. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592
Publication Date:2000
Note:In English
Summary:Two-dimensional multiphase flow experiments were performed in the geotechnical centrifuge centre at Cambridge University to investigate the validity of the centrifuge testing method for evaluating water drainage and LNAPL migration in vadose zone. In this study, four centrifuge tests of LNAPL spillage were performed under an accelerated gravity field of 20 g. One test was performed with a model of homogeneous fine sand, whereas the other had lenses of fine sand and/or silt in a coarser sand deposit. The height of the models was approximately 200 mm, which corresponds to 4 m in prototype scale. Miniature resistivity probes and water tensiometers were placed at various locations of the model to measure the changes in water saturation and pressures during the experiment. Two different LNAPLs were used: (a) Soltrol 220a with dynamic viscosity of 4.8 cP and (b) silicon oil with dynamic viscosity of 19.0 cP. It was found that the dynamic air-water capillary pressure-saturation data obtained in the water drainage stage were similar to the capillary pressure curve measured at 1g tests, indicating that the water drainage behavior follows the geotechnical centrifuge scale. After creating a vadose zone in the model, LNAPL was spilled slightly below the soil surface and the migration and distribution of the oil was monitored for 12.5 days for the Soltrol case and 83.3 days for the Silicon oil case (both in prototype time). The results show that the NAPL migration follows the general centrifuge scaling law under the continuum condition of stable front. When the front became unstable, however, the behavior did not follow the scaling law. Capillary interface effect on NAPL spreading was noticed when the NAPL reached layer interfaces and different entrapment behaviour was observed for different viscosity NAPLs.
Subjects:Capillary pressure; Centrifuge methods; Clastic sediments; Drainage; Experimental studies; Heterogeneity; Light nonaqueous phase liquids; Measurement; Models; Movement; Multiphase flow; Nonaqueous phase liquids; Pollution; Pressure; Sand; Saturation; Sediments; Silt; Soils; Spatial distribution; Testing; Two-dimensional models; Unsaturated zone; Viscosity
Record ID:2003014543
Copyright Information:GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
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