Aging Effect on the S-p relationship due to repeated drying/wetting cycles on the Subsoil

点击翻译按钮获取中文摘要

During FY2019, we continued with the analysis of the changes in the S-p (SWCC) curve of water and an LNAPL (low viscosity paraffin liquid) when subject to repeated water table fluctuations, and participated of some scientific events where we discussed and confirmed some of our findings. Some new ideas were shared for a possible future continuation of this work.As I have left Japan, though, I have to forfeit the remaining of this grant, but the students with whom I worked at Kyoto University will partly continue with this work as part of their research work. This means that, hopefully, part of the remaining objectives of this study can be reached. They will probably be reduced though. In any case, we could work on confirming the following:1. The entry pressure of air-water system is higher than that of air-NAPL system, due to interfacial forces.2. As the changes in residual saturation reduce over time, the largest variations can be find at the beginning of the first drainage cycle, and they seem to follow a decay curve (found previously to be close to Srf(N) = (1 - Srf*) exp(-b N) + Srf*, where Srf* is the final value of residual saturation for the sample, N is the number of cycles, and b is a scaling parameter related to the easiness in reaching stability).3. Irreducible saturation was found to be correlated to initial void ratio and type of fluid.4. The final value of residual saturation is higher in air-NAPL systems than on air-water ones, most probably due to interfacial tension forces.