Abstract

Magnetic resonance imaging (MRI) has recently been proposed as an in situ subsurface imaging technique for locating buried objects in fully hydrated soils. This paper explores the available hydrogen (1H) nuclear magnetic resonance (NMR) signal from water in fully hydrated monodispersed synthetic sands (glass beads) as a predictor of the utility of subsurface MRI. The MRI signal from hydrated soils is a function of three main properties of water in the voids between the soil particles: the spin-lattice relaxation rate (R1), the spin-spin relaxation rate (R2), and the spin density (ρ). The ρ values were measured for random close packed synthetic sands as a function of particle diameter. The R1 and R2, values were measured at a magnetic field strength of 7 Tesla as a function of particle diameter. R1 was also measured as a function of magnetic field strength at 0.235, 2.35, 23.5, and 235 mTesla. The synthetic sands studied have a predictable R1 and R2, and a constant ρ. The water in these sands also has a predictable R1 as a function of applied magnetic field. Therefore, fully hydrated monodispersed real sands are expected to have a predictable NMR signal.

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