A study on the groundwater flow and hydrogeochemical interaction in fractured rock masses

Since the major transport mechanism of radionuclides leaching from a repository is by flowing groundwater, the flow paths, volume and travel time of groundwater in rock mass should be evaluated and convincingly predicted. Hence, the main objectives of this study include: 1) Characterization of the subsurface fracture system developed in rock mass, 2) Evaluation rocks with regard to the retardation mechanism of geological media. A groundwater flow study has been carried out for granitic porphyry occurred in the 2nd Yeonhwa mine which is located in Samchuck, Kangwondo. The fracture system in granitic porphyry has been studied on the basis of the existing surface geologic map and the sketch cards for tunnel geology, and accompanying field investigation. The groundwater system was analyzed by a numerical model of MODIFIED TRAFRAP WT for this study. Results are: 1) The groundwater flow system in fractured rock mass is governed by geological structure and fracture systems. 2) In the mountaineous region, a common feature in the study site, the local flow system is controlled by the amount of precipitation and topographic effects. 3) Jeekyung Dong volcanic rocks consist of tuff, qtz trachyte, rhyolite, andesite and tuffaceous andesite with major minerals of chlorite, smectite illite, chabazite, pyroxene, pl, K-feldspar, hematite, calcite. 4) Pl phenocrysts in tuffs underwent the albitization. Calcite filled partly the secondary pores in pl phenocryst. The porous pumices and glassy materials are partially altered to clay minerals. 5) The phenocrysts in tuff are strongly fractured. Bubbles, dissolved pores and welded textures are observed in tuff. Other volcanic rocks, however, show welded and dense textures. (author)