Premium
Size distributions of pore water and entrapped air during drying‐infiltration processes of sandstone characterized by water‐expulsion porosimetry
Author(s) -
Nishiyama Naoki,
Yokoyama Tadashi,
Takeuchi Shingo
Publication year - 2012
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2011wr011782
Subject(s) - porosimetry , infiltration (hvac) , saturation (graph theory) , porosity , water flow , characterisation of pore space in soil , pore water pressure , airflow , porous medium , hydraulic conductivity , mineralogy , materials science , soil science , composite material , geotechnical engineering , soil water , geology , thermodynamics , physics , mathematics , combinatorics
The transport of pore water in a rock during drying‐infiltration processes was characterized by water‐expulsion porosimetry. In this method, pore water is expelled by increasing gas pressure in a stepwise fashion, and the amounts of water in each pore size class are determined. Fontainebleau sandstone, having an open porosity of 6% and main pore radii of 1–20 μm, was used. The change in size distribution of pore water was determined as a function of the degree of drying. As the drying proceeded, the amount of water decreased first in the larger pores followed by the smaller pores. Next, water was infiltrated into the sample preliminarily adjusted to various water saturations ( S pre‐flow ), and the entrapped air saturation, hydraulic conductivity ( K ), and size distribution of pore water were measured. As S pre‐flow decreased, the entrapped air saturation increased and K decreased as approximated by K ∝ S flow 4.5 , where S flow is the water saturation after the infiltration. A comparison of the size distributions of pore water before and after the infiltration revealed that the ease of water infiltration (air entrapment) depends on pore size. If pores of >8 μm radii were emptied by drying, they were readily refilled with water, whereas smaller pores were only partially refilled because air was trapped in them. The experimentally measured K ‐ S flow relationship generally agreed with those predicted by the Mualem‐van Genuchten model and its modified version accounting for air entrapment, but some differences in the size distribution of pore water were observed between the experiment and the models.