Study On Migration Behavior Of LNAPLs In Soils

Leaking of Light non-aqueous phase liquids (LNAPLs) will result in soiland groundwater pollution, which poses a serious threat to environment andpublic health and welfare. In order to solve the environmental problems, it isimportant to study the transport behavior of LNPALs.The groundwater dynamics and the basic theory of the solute transport aresummarized, and the transport mechanism of LNAPLs in unsaturated soil andthe concept and models of multiphase flow which describe the transportbehaviors of LNAPLs are expatiated.Geotechnical centrifuge modeling can significantly shorten theexperimental time due to scaling law, and has been used effectively to studycontaminant transport in soils. By combining chemical analysis method andimage collection and analyzing system, the transport behaviors of LNAPL inunsaturated are studied by geotechnical centrifuge, in this way, the LNAPLsultimate distribution as well as the transport process of plume are obtained.Numerical analysis is capable of simulating transport behavior ofdifferent time durations and complicated boundary conditions. The finiteelement program is used to model the LNAPLs transport process inhomogeneous and heterogeneous unsaturated soil, and the tempo-spatialconcentration distributions of LNAPLs are obtained which can be contrast withthe results of centrifuge tests', and the sensitivity analysis of some modelparameters is also carried out. Besides, the processes of soil vapor extract andDNAPL transport are properly simulated by numerical analysis.The following conclusions can be made through above work: Thecentrifuge tests of different g-levels give the similar transport behavior ofLNAPL, it shows that high g-level centrifuge test can be used to simulate thelong migration process of LNAPL in unsaturated soils;The real time migrationbehavior of LNAPL was observed by image collection and analyzing system,which can be used to analyze the LNAPLs distribution combined with chemicalanalysis;Numerical analysis can preferable simulate the transport process ofLNAPL and reflect the influence of material characters to transport behavior,whose results are consistent with those of centrifuge tests'. The combination ofgeotechnical centrifuge modeling and numerical analysis is an effectivemethod to study the transport process of contaminants.