Exploring the impact of long-term evaporation on the relationship between capillary pressure and water saturation in unsaturated porous media

JOURNAL OF HYDROLOGY

卷:582

Article

Adegbule, Aderonke O.¹  Kibbey, Tohren C. G.¹ 

[1] Univ Oklahoma, Sch Civil Engn & Environm Sci, 202 W Boyd St,Rm 334, Norman, OK 73019 USA

关键词: Evaporation;    Capillary pressure;    Saturation;    Soil-water characteristic;    Drainage;    Imbibition;   

DOI  :  10.1016/j.jhydrol.2020.124557

来源: Elsevier

【 摘 要 】

The focus of this work was on understanding the impact of evaporation on the capillary pressure-saturation (P-c-S) state of a porous medium. Evaporation is ubiquitous near the ground surface in the vadose zone, but little is known about how evaporation impacts the relationship between capillary pressure and saturation. The hypothesis driving the work was that the P-c-S relationship is the result of an equilibrium between evaporative water loss, capillary forces, and the upward flow of water to replenish evaporated water. Experiments were conducted using two different porous media, a coarse sand and a nylon membrane with a 20 tun pore size. Long-term evaporation experiments were conducted using different configurations to control evaporation within the media. Results found that increased accessibility to evaporation caused saturation in drainage P-c-S curves to decrease over time, causing the curves to become closer to imbibition P-c-S curves. In the membrane, the high external surface area to pore volume ratio caused changes in evaporative flux to produce rapid changes in the P-c-S state of the medium. One implication of the work is that results suggest that long-term drainage experiments in vented columns may not necessarily provide a meaningful measurement of static P-c-S curve, but rather may be impacted by evaporation.

【 授权许可】

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