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

在2019财年，我们继续分析了水和低粘度石蜡液在地下水位反复波动时的S-p(SWCC)曲线的变化，并参加了一些科学活动，讨论并证实了我们的一些发现。大家分享了一些未来可能继续这项工作的新想法。不过，由于我已经离开日本，我不得不放弃剩余的这笔补助金，但与我一起在京都大学工作的学生将部分继续这项工作，作为他们研究工作的一部分。这意味着，这项研究的剩余目标有望部分实现。不过，它们可能会减少。在任何情况下，我们都可以确定以下几点：1.由于界面作用力，空气-水系统的入口压力高于空气-NAPL系统的入口压力。随着剩余饱和度的变化随着时间的推移而减小，最大的变化可以在第一个排水周期的开始处找到，并且它们似乎遵循一条衰减曲线(先前发现接近于SRF(N)=(1-SRF*)exp(-b N)SRF*，其中SRF*是样品的剩余饱和度的最终值，N是循环次数，b是与达到稳定的难易程度有关的尺度参数)。束缚饱和度与初始孔隙率和流体类型有关。在空气-NAPL体系中，残余饱和度的终值高于空气-水体系，这很可能是由于界面张力所致。

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.