Journal Published Online: 06 December 2023
Volume 47, Issue 3

An NMR-Based Procedure for Evaluating the Apparent Surface Relaxivity and Pore Size Distribution of Soils

CODEN: GTJODJ

Abstract

A nuclear magnetic resonance–based procedure is proposed to evaluate the surface relaxivity parameters ρk (k = 1 or 2 for spin-lattice or spin-spin relaxation) and pore size distributions (PSDs) of six different soils, including four expansive clays, a silt, and a loess. It is shown that both ρ1 and ρ2 first increases with specific water content (w) until w increases up to about 10 %, and then ρ1 approaches a stable value, whereas ρ2 slightly decreases. The underlying mechanisms for the surface relaxation of water protons are evaluated. It is shown that the water proton relaxation in expansive clays is controlled by the partially fixed ions confined in diffuse double layers, whereas that in silt and loess is dictated by the proton exchange between water molecules and surface hydroxyls and the dipole–dipole interaction between water molecules and hydrogen-bonding molecules. As a consequence, the ρk values of silt and loess are larger than those of expansive clays. A new method is proposed to determine the apparent surface relaxivity parameter that is used to determine the PSD of soil based on the surface relaxation time distribution. The proposed procedure is validated by comparing the estimated PSDs with the measurements of mercury intrusion porosimetry.

Author Information

Tian, Huihui
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei, P. R. China
Wu, Guangshui
Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering, Guilin University of Technology, Qixing District, Guilin, P. R. China
Wei, Changfu
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei, P. R. China
Pages: 15
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Stock #: GTJ20230395
ISSN: 0149-6115
DOI: 10.1520/GTJ20230395