Abstract: It is difficult to determinate the transient water content (suction) distribution in geomaterials rapidly and accurately during the permeability test of unsaturated soils. Ordinary water content measurement methods are not only time-consuming but also cumbersome with the traditional relative large probes bonded with the specimen, likely posing destructive effects on the test sample. In this paper, the water content in white Portland cement specimen was measured swiftly and non-destructively by employing the nuclear magnetic resonance (NMR) technology. The unsaturated permeability coefficients of white Portland cement were obtained by the instantaneous profile method. Results showed that the unsaturated hydraulic conductivity of white Portland cement varied greatly with suction, ranging from 4.61×10^-12 to 7.59×10^-8 m/s; when suction was higher than 1 MPa, hydraulic conductivity increased slowly with suction decreasing; while as suction reduced below 1 MPa, hydraulic conductivity showed a steep increase by several orders of magnitude. Compared with traditional technology, NMR technology is more applicable in measuring the water content distribution in permeability test of non-saturated soil.

Key words: unsaturated soil, NMR technology, unsaturated permeability, instantaneous profile method, water content, suction