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

在2019财年，我们继续分析了水位反复波动时水和低粘度石蜡液体S-p （SWCC）曲线的变化，并参加了一些科学活动，讨论和证实了我们的一些发现。大家就今后可能继续进行这项工作分享了一些新的想法。由于我已经离开了日本，我不得不放弃剩余的资助，但我在京都大学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，本研究的部分剩余目标有望实现。但它们可能会减少。无论如何，我们可以努力确认以下几点：由于界面作用力的作用，空气-水系统的入口压力比空气- napl系统的入口压力要高。随着时间的推移，残余饱和度的变化减小，在第一个排水循环开始时变化最大，它们似乎遵循一个衰减曲线(之前发现接近于Srf(N) = （1 - Srf*) exp(-b N) + Srf*，其中Srf*为样品的残余饱和度的最终值，N为循环次数，b是与是否容易达到稳定性相关的缩放参数）。不可还原饱和度与初始孔隙比和流体类型有关。空气- napl体系的残余饱和度最终值高于空气-水体系，这很可能是由于界面张力的作用。

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.