Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

This paper shows the results of recent study concerning the changes in mineralogical and petrological properties of gneissic rocks due to weathering. Textural variations and changes in physical properties were also investigated on both field samples of different weathering grades, and fresh rock cores subjected to various artificial weathering environments. Chemical weathering indices, such as the weathering potential index and the weathering product index, were measured. The gneissic rock mass shows several structural complexities related to the metamorphic processes. The presence of these features apparently has greater effects on developing differentiated weathering zones than the depth from the free surface dose. The effects of various agents, such as temperature, water, acid, and salt, on weathering of gneissic rocks were investigated. Physical properties, including porosity, absorption, uniaxial compressive strength, tensile strength and P-wave velocity were measured. Soaking in acid showed remarkable change in the physical properties of specimens; porosity and absorption increased, and tensile strength decreased. From the XRF analysis, SiO2 increased with increasing weathering grade, while Fe2O3 , TiO2 , MnO, CaO, MgO and P2O5 decreased. Decomposition of feldspars and resulting clay minerals such as kaolinite and illite were observed in highly weathered samples. It seemed to be possible to reference weathering grades for gneissic rocks from good correlations of WPI-WP, and Imob - WP(PI).