PHYSICAL PROPERTIES OF SOME KOREAN GRANITES IN EARLY STAGES OF WEATHERING

To understand the weathering processes of some granites, fresh and weathered Jurassic granites were collected systematically from some stone and agggregate quarries in Korea. Sampled rocks were classified by their weathering grades of I to VI through field and basic laboratory tests and then physical properties, which are thought to be closely related with weathering, such as apparent density, porosity, absorption, P-wave velocity, resistivity and uniaxial compressive strength were measured. Also abundances of major elements were analyzed to investigate their variations and their applicability to weathering indices. Variations of physical properties of granites through weathering processes are well shown in the patterns of normalized properties to those of their corresponding fresh ones. Apparent specific gravities for fresh granites are in the range of 2.60 to 2.65 and as weathering grades become higher, those for weathered granites deacrease gradually down to the range of 2.47 to 2.61 for the highly weathered samples. Through weathering absorption and porosity increased continuously up to 3 to 5 times when the highly weathered samples are compared with the fresh ones. The velocities of the P-wave through granite samples decrease gradually down to lower than 2,000m/sec for the highly weathered granites. Compressive strengths of granites, which are known to be related with quartz content and grain size, decrease significantly through weathering. Variations in resitivities of granites through weathering do not show a regular trend but generally fine-grained granite samples of low porosity and absorption show lower resitivities in comparision with those of other coarser-grained ones. As weathering proceeds, some physical properties such as porosity, absorption, P-wave velocity and compressive strength vary significantly to be potential indicators of the degree of weathering of Korean granites. Among the reviewed chemical indices of weathering, the WPI (weathering potential index) and the iron oxidation ratio show significant varations and consistent trends through weathering and therefore, these indices can indicate the weathering degree of granites.