A NMR technique for the analysis of pore structure: Determination of continuous pore size distributions

Influence of drying–wetting cycles on soil-water characteristic curve of undisturbed granite residual soils and microstructure mechanism by nuclear magnetic resonance (NMR) spin-spin relaxation time (T2) relaxometry

“…Some researches obtained ρ 2 values by comparing the T 2 relaxation distribution with POSD data calculated by MIP (Marschall et al 1995;Kleinberg 1996;Kenyon 1997;Li et al 2008;Minagawa, et al 2008; Yao and Liu 2012), Nitrogen Gas Adsorption or Diffusion measurements (Gallegos and Smith 1988;Hurlimann et al 1994;Sorland et al 2007), Cation Exchange Capacity (Sen et al 1990), Differential Thermal Calorimetry (Ramia et al 2010) and Photo Microscopy or Image Analysis (Howard et al 1993;Kenyon 1997;Arns 2004;Wang 2009) by Kenyon et al (1988), is used to obtain the surface relaxivity coefficient (ρ 2 ) which is…”

“…Desiccation may cause irreversible changes in pore structure, which in turn will affect the actual POSD of the soils. The Image analysis or Microscopy requires approach a large quantity of two-dimensional information for the desired three-dimensional pore structure information and it is time-consuming (Gallegos and Smith 1988;Hinedi et al 1997;Giesche 2006;Kate and Gokhale 2006;Minagawa, et al 2008;Benjamini et al 2014;Wang et al 2016). None of those methods are suitable for this present study because the tested soil is a special kind of low density (dry density, ρ d =1.30 g/cm 3 ) granite residual soil with grain size distribution ranging from gravel to clay.…”

“…It is well known that the amplitude of the proton NMR signal is proportional to the fluid content and that relaxation times give information on the POSD. Though NMR techniques are extensively used in petroleum industry and medical science, recently it has been used successfully in soil mechanics, such as, to quantify and estimate the amount of water in soils, to evaluate porosity, POSD and hydraulic conductivity, to characterize hydraulic processes of unsaturated soils or characterizing the vadose zone and pore water distribution and migration at various sections of hydraulic cycles (Gallegos and Smith 1988;Akporiaye et al 1994;Strange et al 1993;Milia et al 1998;Yun et al 2002;Bird et al 2005;He et al 2005;Mohnke and Yaramanci 2008;Jaeger et al 2009;Stingaciu et al 2010;Ramia et al 2010;Costabel and Yaramanci 2013;Tian et al 2014;Walsh et al 2014). NMR technique is also applied to investigate the POSDs of permafrost and gas hydrate sediments ( drying-wetting cycles on SWCC of undisturbed granite residual soils.…”

Methane Hydrate Production From Alaskan Permafrost

“…Rocks and sediments generally have very broad distributions of pore sizes, and therefore magnetization decays can be expressed as a sum of exponential decays [Gallegos and Smith, 1988]:…”

“…Therefore, the set of 50 m(T 2i ) was found using a regularized nonlinear leastsquares technique that renders the results smooth and stable in the presence of random noise [Butler et al, 1981]. The function m(T 2 ), conventionally called a T 2 distribution, maps linearly to a volumetrically weighted distribution of pore sizes [Gallegos and Smith, 1988;Kleinberg, 1999]. …”