This paper describes moisture movement in unsaturated sandstone and tuff, whose porosities are 13% and 29% respectively. For each rock three cylindrical specimens are prepared: dry (not perfectly) and saturated intact specimens, and one dry specimen including a tensile fracture parallel to the cylindrical axis. The side surface is sealed with silicon sealant to allow one dimensional movement of moisture. The 1cm lower part of the specimen is submerged in water, and the top surface is open to the room air. In this condition, water is infiltrated into the dry specimen upwards while the top surface of the initially saturated specimen becomes dry with time. During the experiments, relative humidity at two different heights above the top surface is monitored as well as total weight of the specimen. An evaporation rate is calculated from the difference between the two values of relative humidity, based on a molecular diffusion theory. In addition, water absorption at the top surface is measured using an infrared optical moisture meter. The experiments show that a steady state is not reached even in 70 days after the beginning of infiltration into the intact specimen. However, the changes of weight can be predicted with the data for the first 10 days, by a hyperbolic function which has two parameters giving a infiltration rate at the beginning of the experiment and weight at the steady state. The evaporation rate and the infiltration rate of intact sandstone are different from those of intact tuff, but each difference is not so large as that of the porosities. Distributions of saturation in the specimens are obtained from the results of the changes of weight and moisture at the top surfaces, which present increasing degrees of saturation with depth. When a two layer model composed of dry and capillary zones is used to estimate the evaporation rate in a drying process, the estimated value may include about a 50% error.
