The importance of the application of unsaturated soil mechanics in geotechnical engineering design has been well understood. However, time consumption and neediness of specific laboratory testing apparatus in measuring unsaturated soil properties have limited the application of unsaturated soil mechanics theories into practice. Though, the methods for predicting unsaturated soil properties have been developed, the verification for these methods for wide range of soil types is required to

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... e in practicing engineers' confidence in using these methods. In this study, a new permeameter was developed to measure the hydraulic conductivity of unsaturated soils using the steady state method and direct measured suction (negative pore-water pressure) values. The apparatus is instrumented with two tensiometers for direct measurement of suction during the test. The apparatus can be used to obtain the hydraulic conductivity function of sandy soil over a low suction range (0 ~ 10 kPa). First, the repeatability of the unsaturated hydraulic conductivity measurement using the new permeameter was verified by conducting the tests on two identical sandy soil specimens and obtaining similar results. The hydraulic conductivity functions of two sandy soils were then measured during the drying and wetting processes of soils. A significant hysteresis was observed when the hydraulic conductivity was plotted against the suction. However, hysteresis effects were not apparent, when it was plotted against volumetric water content. Further, the measured unsaturated hydraulic conductivity functions were compared with its prediction using three different predictive methods that are widely incorporated into numerical software. The results suggested that these predictive methods could be capable of capturing the measured behavior with reasonable agreement.