On the Change of Elastic Wave Velocities and Uniaxial Compressive Strength of Sandstone and Andesite by Condition of Drying

It is necessary for measurment of moisture content and porosity to define the dry condition of rock samples. Nevertheless various coditions of drying are actually adopted by many peoples.In this paper, the weight of samples, velocities of elastic waves and uniaxial complessive strength of rock specimens were measured at seven different condition of drying which are 50, 75, 105, 125, 150°C constant temperature for 48 hours, kept in desicator contained silicagel for a month, and dried naturall in the room.Sandstone and andestite have a different tendency of change in measured values. Results obtained in this paper are summarized as follows:(1) In regard to the change of weight, a remarkable effect of drying is showed at 50°C constant temperature dring for andesite which have higher porosity, and showed barely a constant weightat drying over 105°C for sandstone which has lower porosity. The drying in desicator contained silicagel has a similar effect at 50°C oven drying for andesite and 75°C for sandstone.(2) Dillatational waves of specimen show a maximum velocity at 50, 75°C drying forandesite, at 75, 105°C and silicagel drying for sandstone. Increase of the velocities for both rocks become dull at drying over 125°C Velocities of longitudinal vibration show a similar tendency of the dilatational waves for andesite, and show a maximum value at 105°C and silicagel drying.(3) Compressive strength of both rocks shows an increase in the region from room temperature to 150°C drying. Compressive strength for andesite fairly increases at 50°C drying, and that for sandstone shows a remarkable increment at 105°C drying. Compressive strength at silicagel drying shows a similar tendency of velocities.